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lock.c
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1 /*-------------------------------------------------------------------------
2  *
3  * lock.c
4  * POSTGRES primary lock mechanism
5  *
6  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  *
10  * IDENTIFICATION
11  * src/backend/storage/lmgr/lock.c
12  *
13  * NOTES
14  * A lock table is a shared memory hash table. When
15  * a process tries to acquire a lock of a type that conflicts
16  * with existing locks, it is put to sleep using the routines
17  * in storage/lmgr/proc.c.
18  *
19  * For the most part, this code should be invoked via lmgr.c
20  * or another lock-management module, not directly.
21  *
22  * Interface:
23  *
24  * InitLocks(), GetLocksMethodTable(), GetLockTagsMethodTable(),
25  * LockAcquire(), LockRelease(), LockReleaseAll(),
26  * LockCheckConflicts(), GrantLock()
27  *
28  *-------------------------------------------------------------------------
29  */
30 #include "postgres.h"
31 
32 #include <signal.h>
33 #include <unistd.h>
34 
35 #include "access/transam.h"
36 #include "access/twophase.h"
37 #include "access/twophase_rmgr.h"
38 #include "access/xlog.h"
39 #include "access/xlogutils.h"
40 #include "miscadmin.h"
41 #include "pg_trace.h"
42 #include "storage/proc.h"
43 #include "storage/procarray.h"
44 #include "storage/sinvaladt.h"
45 #include "storage/spin.h"
46 #include "storage/standby.h"
47 #include "utils/memutils.h"
48 #include "utils/ps_status.h"
49 #include "utils/resowner.h"
50 
51 
52 /* This configuration variable is used to set the lock table size */
53 int max_locks_per_xact; /* set by guc.c */
54 
55 #define NLOCKENTS() \
56  mul_size(max_locks_per_xact, add_size(MaxBackends, max_prepared_xacts))
57 
58 
59 /*
60  * Data structures defining the semantics of the standard lock methods.
61  *
62  * The conflict table defines the semantics of the various lock modes.
63  */
64 static const LOCKMASK LockConflicts[] = {
65  0,
66 
67  /* AccessShareLock */
69 
70  /* RowShareLock */
72 
73  /* RowExclusiveLock */
76 
77  /* ShareUpdateExclusiveLock */
81 
82  /* ShareLock */
86 
87  /* ShareRowExclusiveLock */
91 
92  /* ExclusiveLock */
97 
98  /* AccessExclusiveLock */
103 
104 };
105 
106 /* Names of lock modes, for debug printouts */
107 static const char *const lock_mode_names[] =
108 {
109  "INVALID",
110  "AccessShareLock",
111  "RowShareLock",
112  "RowExclusiveLock",
113  "ShareUpdateExclusiveLock",
114  "ShareLock",
115  "ShareRowExclusiveLock",
116  "ExclusiveLock",
117  "AccessExclusiveLock"
118 };
119 
120 #ifndef LOCK_DEBUG
121 static bool Dummy_trace = false;
122 #endif
123 
125  MaxLockMode,
128 #ifdef LOCK_DEBUG
129  &Trace_locks
130 #else
131  &Dummy_trace
132 #endif
133 };
134 
136  MaxLockMode,
139 #ifdef LOCK_DEBUG
140  &Trace_userlocks
141 #else
142  &Dummy_trace
143 #endif
144 };
145 
146 /*
147  * map from lock method id to the lock table data structures
148  */
149 static const LockMethod LockMethods[] = {
150  NULL,
153 };
154 
155 
156 /* Record that's written to 2PC state file when a lock is persisted */
157 typedef struct TwoPhaseLockRecord
158 {
162 
163 
164 /*
165  * Count of the number of fast path lock slots we believe to be used. This
166  * might be higher than the real number if another backend has transferred
167  * our locks to the primary lock table, but it can never be lower than the
168  * real value, since only we can acquire locks on our own behalf.
169  */
170 static int FastPathLocalUseCount = 0;
171 
172 /*
173  * Flag to indicate if the relation extension lock is held by this backend.
174  * This flag is used to ensure that while holding the relation extension lock
175  * we don't try to acquire a heavyweight lock on any other object. This
176  * restriction implies that the relation extension lock won't ever participate
177  * in the deadlock cycle because we can never wait for any other heavyweight
178  * lock after acquiring this lock.
179  *
180  * Such a restriction is okay for relation extension locks as unlike other
181  * heavyweight locks these are not held till the transaction end. These are
182  * taken for a short duration to extend a particular relation and then
183  * released.
184  */
185 static bool IsRelationExtensionLockHeld PG_USED_FOR_ASSERTS_ONLY = false;
186 
187 /* Macros for manipulating proc->fpLockBits */
188 #define FAST_PATH_BITS_PER_SLOT 3
189 #define FAST_PATH_LOCKNUMBER_OFFSET 1
190 #define FAST_PATH_MASK ((1 << FAST_PATH_BITS_PER_SLOT) - 1)
191 #define FAST_PATH_GET_BITS(proc, n) \
192  (((proc)->fpLockBits >> (FAST_PATH_BITS_PER_SLOT * n)) & FAST_PATH_MASK)
193 #define FAST_PATH_BIT_POSITION(n, l) \
194  (AssertMacro((l) >= FAST_PATH_LOCKNUMBER_OFFSET), \
195  AssertMacro((l) < FAST_PATH_BITS_PER_SLOT+FAST_PATH_LOCKNUMBER_OFFSET), \
196  AssertMacro((n) < FP_LOCK_SLOTS_PER_BACKEND), \
197  ((l) - FAST_PATH_LOCKNUMBER_OFFSET + FAST_PATH_BITS_PER_SLOT * (n)))
198 #define FAST_PATH_SET_LOCKMODE(proc, n, l) \
199  (proc)->fpLockBits |= UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l)
200 #define FAST_PATH_CLEAR_LOCKMODE(proc, n, l) \
201  (proc)->fpLockBits &= ~(UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l))
202 #define FAST_PATH_CHECK_LOCKMODE(proc, n, l) \
203  ((proc)->fpLockBits & (UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l)))
204 
205 /*
206  * The fast-path lock mechanism is concerned only with relation locks on
207  * unshared relations by backends bound to a database. The fast-path
208  * mechanism exists mostly to accelerate acquisition and release of locks
209  * that rarely conflict. Because ShareUpdateExclusiveLock is
210  * self-conflicting, it can't use the fast-path mechanism; but it also does
211  * not conflict with any of the locks that do, so we can ignore it completely.
212  */
213 #define EligibleForRelationFastPath(locktag, mode) \
214  ((locktag)->locktag_lockmethodid == DEFAULT_LOCKMETHOD && \
215  (locktag)->locktag_type == LOCKTAG_RELATION && \
216  (locktag)->locktag_field1 == MyDatabaseId && \
217  MyDatabaseId != InvalidOid && \
218  (mode) < ShareUpdateExclusiveLock)
219 #define ConflictsWithRelationFastPath(locktag, mode) \
220  ((locktag)->locktag_lockmethodid == DEFAULT_LOCKMETHOD && \
221  (locktag)->locktag_type == LOCKTAG_RELATION && \
222  (locktag)->locktag_field1 != InvalidOid && \
223  (mode) > ShareUpdateExclusiveLock)
224 
225 static bool FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode);
226 static bool FastPathUnGrantRelationLock(Oid relid, LOCKMODE lockmode);
227 static bool FastPathTransferRelationLocks(LockMethod lockMethodTable,
228  const LOCKTAG *locktag, uint32 hashcode);
230 
231 /*
232  * To make the fast-path lock mechanism work, we must have some way of
233  * preventing the use of the fast-path when a conflicting lock might be present.
234  * We partition* the locktag space into FAST_PATH_STRONG_LOCK_HASH_PARTITIONS,
235  * and maintain an integer count of the number of "strong" lockers
236  * in each partition. When any "strong" lockers are present (which is
237  * hopefully not very often), the fast-path mechanism can't be used, and we
238  * must fall back to the slower method of pushing matching locks directly
239  * into the main lock tables.
240  *
241  * The deadlock detector does not know anything about the fast path mechanism,
242  * so any locks that might be involved in a deadlock must be transferred from
243  * the fast-path queues to the main lock table.
244  */
245 
246 #define FAST_PATH_STRONG_LOCK_HASH_BITS 10
247 #define FAST_PATH_STRONG_LOCK_HASH_PARTITIONS \
248  (1 << FAST_PATH_STRONG_LOCK_HASH_BITS)
249 #define FastPathStrongLockHashPartition(hashcode) \
250  ((hashcode) % FAST_PATH_STRONG_LOCK_HASH_PARTITIONS)
251 
252 typedef struct
253 {
257 
259 
260 
261 /*
262  * Pointers to hash tables containing lock state
263  *
264  * The LockMethodLockHash and LockMethodProcLockHash hash tables are in
265  * shared memory; LockMethodLocalHash is local to each backend.
266  */
270 
271 
272 /* private state for error cleanup */
276 
277 
278 #ifdef LOCK_DEBUG
279 
280 /*------
281  * The following configuration options are available for lock debugging:
282  *
283  * TRACE_LOCKS -- give a bunch of output what's going on in this file
284  * TRACE_USERLOCKS -- same but for user locks
285  * TRACE_LOCK_OIDMIN-- do not trace locks for tables below this oid
286  * (use to avoid output on system tables)
287  * TRACE_LOCK_TABLE -- trace locks on this table (oid) unconditionally
288  * DEBUG_DEADLOCKS -- currently dumps locks at untimely occasions ;)
289  *
290  * Furthermore, but in storage/lmgr/lwlock.c:
291  * TRACE_LWLOCKS -- trace lightweight locks (pretty useless)
292  *
293  * Define LOCK_DEBUG at compile time to get all these enabled.
294  * --------
295  */
296 
297 int Trace_lock_oidmin = FirstNormalObjectId;
298 bool Trace_locks = false;
299 bool Trace_userlocks = false;
300 int Trace_lock_table = 0;
301 bool Debug_deadlocks = false;
302 
303 
304 inline static bool
305 LOCK_DEBUG_ENABLED(const LOCKTAG *tag)
306 {
307  return
309  ((Oid) tag->locktag_field2 >= (Oid) Trace_lock_oidmin))
310  || (Trace_lock_table &&
311  (tag->locktag_field2 == Trace_lock_table));
312 }
313 
314 
315 inline static void
316 LOCK_PRINT(const char *where, const LOCK *lock, LOCKMODE type)
317 {
318  if (LOCK_DEBUG_ENABLED(&lock->tag))
319  elog(LOG,
320  "%s: lock(%p) id(%u,%u,%u,%u,%u,%u) grantMask(%x) "
321  "req(%d,%d,%d,%d,%d,%d,%d)=%d "
322  "grant(%d,%d,%d,%d,%d,%d,%d)=%d wait(%d) type(%s)",
323  where, lock,
324  lock->tag.locktag_field1, lock->tag.locktag_field2,
325  lock->tag.locktag_field3, lock->tag.locktag_field4,
327  lock->grantMask,
328  lock->requested[1], lock->requested[2], lock->requested[3],
329  lock->requested[4], lock->requested[5], lock->requested[6],
330  lock->requested[7], lock->nRequested,
331  lock->granted[1], lock->granted[2], lock->granted[3],
332  lock->granted[4], lock->granted[5], lock->granted[6],
333  lock->granted[7], lock->nGranted,
334  dclist_count(&lock->waitProcs),
335  LockMethods[LOCK_LOCKMETHOD(*lock)]->lockModeNames[type]);
336 }
337 
338 
339 inline static void
340 PROCLOCK_PRINT(const char *where, const PROCLOCK *proclockP)
341 {
342  if (LOCK_DEBUG_ENABLED(&proclockP->tag.myLock->tag))
343  elog(LOG,
344  "%s: proclock(%p) lock(%p) method(%u) proc(%p) hold(%x)",
345  where, proclockP, proclockP->tag.myLock,
346  PROCLOCK_LOCKMETHOD(*(proclockP)),
347  proclockP->tag.myProc, (int) proclockP->holdMask);
348 }
349 #else /* not LOCK_DEBUG */
350 
351 #define LOCK_PRINT(where, lock, type) ((void) 0)
352 #define PROCLOCK_PRINT(where, proclockP) ((void) 0)
353 #endif /* not LOCK_DEBUG */
354 
355 
356 static uint32 proclock_hash(const void *key, Size keysize);
357 static void RemoveLocalLock(LOCALLOCK *locallock);
358 static PROCLOCK *SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc,
359  const LOCKTAG *locktag, uint32 hashcode, LOCKMODE lockmode);
360 static void GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner);
361 static void BeginStrongLockAcquire(LOCALLOCK *locallock, uint32 fasthashcode);
362 static void FinishStrongLockAcquire(void);
363 static void WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner,
364  bool dontWait);
365 static void ReleaseLockIfHeld(LOCALLOCK *locallock, bool sessionLock);
366 static void LockReassignOwner(LOCALLOCK *locallock, ResourceOwner parent);
367 static bool UnGrantLock(LOCK *lock, LOCKMODE lockmode,
368  PROCLOCK *proclock, LockMethod lockMethodTable);
369 static void CleanUpLock(LOCK *lock, PROCLOCK *proclock,
370  LockMethod lockMethodTable, uint32 hashcode,
371  bool wakeupNeeded);
372 static void LockRefindAndRelease(LockMethod lockMethodTable, PGPROC *proc,
373  LOCKTAG *locktag, LOCKMODE lockmode,
374  bool decrement_strong_lock_count);
375 static void GetSingleProcBlockerStatusData(PGPROC *blocked_proc,
377 
378 
379 /*
380  * InitLocks -- Initialize the lock manager's data structures.
381  *
382  * This is called from CreateSharedMemoryAndSemaphores(), which see for
383  * more comments. In the normal postmaster case, the shared hash tables
384  * are created here, as well as a locallock hash table that will remain
385  * unused and empty in the postmaster itself. Backends inherit the pointers
386  * to the shared tables via fork(), and also inherit an image of the locallock
387  * hash table, which they proceed to use. In the EXEC_BACKEND case, each
388  * backend re-executes this code to obtain pointers to the already existing
389  * shared hash tables and to create its locallock hash table.
390  */
391 void
393 {
394  HASHCTL info;
395  long init_table_size,
396  max_table_size;
397  bool found;
398 
399  /*
400  * Compute init/max size to request for lock hashtables. Note these
401  * calculations must agree with LockShmemSize!
402  */
403  max_table_size = NLOCKENTS();
404  init_table_size = max_table_size / 2;
405 
406  /*
407  * Allocate hash table for LOCK structs. This stores per-locked-object
408  * information.
409  */
410  info.keysize = sizeof(LOCKTAG);
411  info.entrysize = sizeof(LOCK);
413 
414  LockMethodLockHash = ShmemInitHash("LOCK hash",
415  init_table_size,
416  max_table_size,
417  &info,
419 
420  /* Assume an average of 2 holders per lock */
421  max_table_size *= 2;
422  init_table_size *= 2;
423 
424  /*
425  * Allocate hash table for PROCLOCK structs. This stores
426  * per-lock-per-holder information.
427  */
428  info.keysize = sizeof(PROCLOCKTAG);
429  info.entrysize = sizeof(PROCLOCK);
430  info.hash = proclock_hash;
432 
433  LockMethodProcLockHash = ShmemInitHash("PROCLOCK hash",
434  init_table_size,
435  max_table_size,
436  &info,
438 
439  /*
440  * Allocate fast-path structures.
441  */
443  ShmemInitStruct("Fast Path Strong Relation Lock Data",
444  sizeof(FastPathStrongRelationLockData), &found);
445  if (!found)
447 
448  /*
449  * Allocate non-shared hash table for LOCALLOCK structs. This stores lock
450  * counts and resource owner information.
451  *
452  * The non-shared table could already exist in this process (this occurs
453  * when the postmaster is recreating shared memory after a backend crash).
454  * If so, delete and recreate it. (We could simply leave it, since it
455  * ought to be empty in the postmaster, but for safety let's zap it.)
456  */
459 
460  info.keysize = sizeof(LOCALLOCKTAG);
461  info.entrysize = sizeof(LOCALLOCK);
462 
463  LockMethodLocalHash = hash_create("LOCALLOCK hash",
464  16,
465  &info,
467 }
468 
469 
470 /*
471  * Fetch the lock method table associated with a given lock
472  */
475 {
476  LOCKMETHODID lockmethodid = LOCK_LOCKMETHOD(*lock);
477 
478  Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
479  return LockMethods[lockmethodid];
480 }
481 
482 /*
483  * Fetch the lock method table associated with a given locktag
484  */
487 {
488  LOCKMETHODID lockmethodid = (LOCKMETHODID) locktag->locktag_lockmethodid;
489 
490  Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
491  return LockMethods[lockmethodid];
492 }
493 
494 
495 /*
496  * Compute the hash code associated with a LOCKTAG.
497  *
498  * To avoid unnecessary recomputations of the hash code, we try to do this
499  * just once per function, and then pass it around as needed. Aside from
500  * passing the hashcode to hash_search_with_hash_value(), we can extract
501  * the lock partition number from the hashcode.
502  */
503 uint32
504 LockTagHashCode(const LOCKTAG *locktag)
505 {
506  return get_hash_value(LockMethodLockHash, (const void *) locktag);
507 }
508 
509 /*
510  * Compute the hash code associated with a PROCLOCKTAG.
511  *
512  * Because we want to use just one set of partition locks for both the
513  * LOCK and PROCLOCK hash tables, we have to make sure that PROCLOCKs
514  * fall into the same partition number as their associated LOCKs.
515  * dynahash.c expects the partition number to be the low-order bits of
516  * the hash code, and therefore a PROCLOCKTAG's hash code must have the
517  * same low-order bits as the associated LOCKTAG's hash code. We achieve
518  * this with this specialized hash function.
519  */
520 static uint32
521 proclock_hash(const void *key, Size keysize)
522 {
523  const PROCLOCKTAG *proclocktag = (const PROCLOCKTAG *) key;
524  uint32 lockhash;
525  Datum procptr;
526 
527  Assert(keysize == sizeof(PROCLOCKTAG));
528 
529  /* Look into the associated LOCK object, and compute its hash code */
530  lockhash = LockTagHashCode(&proclocktag->myLock->tag);
531 
532  /*
533  * To make the hash code also depend on the PGPROC, we xor the proc
534  * struct's address into the hash code, left-shifted so that the
535  * partition-number bits don't change. Since this is only a hash, we
536  * don't care if we lose high-order bits of the address; use an
537  * intermediate variable to suppress cast-pointer-to-int warnings.
538  */
539  procptr = PointerGetDatum(proclocktag->myProc);
540  lockhash ^= ((uint32) procptr) << LOG2_NUM_LOCK_PARTITIONS;
541 
542  return lockhash;
543 }
544 
545 /*
546  * Compute the hash code associated with a PROCLOCKTAG, given the hashcode
547  * for its underlying LOCK.
548  *
549  * We use this just to avoid redundant calls of LockTagHashCode().
550  */
551 static inline uint32
552 ProcLockHashCode(const PROCLOCKTAG *proclocktag, uint32 hashcode)
553 {
554  uint32 lockhash = hashcode;
555  Datum procptr;
556 
557  /*
558  * This must match proclock_hash()!
559  */
560  procptr = PointerGetDatum(proclocktag->myProc);
561  lockhash ^= ((uint32) procptr) << LOG2_NUM_LOCK_PARTITIONS;
562 
563  return lockhash;
564 }
565 
566 /*
567  * Given two lock modes, return whether they would conflict.
568  */
569 bool
571 {
572  LockMethod lockMethodTable = LockMethods[DEFAULT_LOCKMETHOD];
573 
574  if (lockMethodTable->conflictTab[mode1] & LOCKBIT_ON(mode2))
575  return true;
576 
577  return false;
578 }
579 
580 /*
581  * LockHeldByMe -- test whether lock 'locktag' is held with mode 'lockmode'
582  * by the current transaction
583  */
584 bool
585 LockHeldByMe(const LOCKTAG *locktag, LOCKMODE lockmode)
586 {
587  LOCALLOCKTAG localtag;
588  LOCALLOCK *locallock;
589 
590  /*
591  * See if there is a LOCALLOCK entry for this lock and lockmode
592  */
593  MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
594  localtag.lock = *locktag;
595  localtag.mode = lockmode;
596 
597  locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
598  &localtag,
599  HASH_FIND, NULL);
600 
601  return (locallock && locallock->nLocks > 0);
602 }
603 
604 #ifdef USE_ASSERT_CHECKING
605 /*
606  * GetLockMethodLocalHash -- return the hash of local locks, for modules that
607  * evaluate assertions based on all locks held.
608  */
609 HTAB *
610 GetLockMethodLocalHash(void)
611 {
612  return LockMethodLocalHash;
613 }
614 #endif
615 
616 /*
617  * LockHasWaiters -- look up 'locktag' and check if releasing this
618  * lock would wake up other processes waiting for it.
619  */
620 bool
621 LockHasWaiters(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock)
622 {
623  LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
624  LockMethod lockMethodTable;
625  LOCALLOCKTAG localtag;
626  LOCALLOCK *locallock;
627  LOCK *lock;
628  PROCLOCK *proclock;
629  LWLock *partitionLock;
630  bool hasWaiters = false;
631 
632  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
633  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
634  lockMethodTable = LockMethods[lockmethodid];
635  if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
636  elog(ERROR, "unrecognized lock mode: %d", lockmode);
637 
638 #ifdef LOCK_DEBUG
639  if (LOCK_DEBUG_ENABLED(locktag))
640  elog(LOG, "LockHasWaiters: lock [%u,%u] %s",
641  locktag->locktag_field1, locktag->locktag_field2,
642  lockMethodTable->lockModeNames[lockmode]);
643 #endif
644 
645  /*
646  * Find the LOCALLOCK entry for this lock and lockmode
647  */
648  MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
649  localtag.lock = *locktag;
650  localtag.mode = lockmode;
651 
652  locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
653  &localtag,
654  HASH_FIND, NULL);
655 
656  /*
657  * let the caller print its own error message, too. Do not ereport(ERROR).
658  */
659  if (!locallock || locallock->nLocks <= 0)
660  {
661  elog(WARNING, "you don't own a lock of type %s",
662  lockMethodTable->lockModeNames[lockmode]);
663  return false;
664  }
665 
666  /*
667  * Check the shared lock table.
668  */
669  partitionLock = LockHashPartitionLock(locallock->hashcode);
670 
671  LWLockAcquire(partitionLock, LW_SHARED);
672 
673  /*
674  * We don't need to re-find the lock or proclock, since we kept their
675  * addresses in the locallock table, and they couldn't have been removed
676  * while we were holding a lock on them.
677  */
678  lock = locallock->lock;
679  LOCK_PRINT("LockHasWaiters: found", lock, lockmode);
680  proclock = locallock->proclock;
681  PROCLOCK_PRINT("LockHasWaiters: found", proclock);
682 
683  /*
684  * Double-check that we are actually holding a lock of the type we want to
685  * release.
686  */
687  if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
688  {
689  PROCLOCK_PRINT("LockHasWaiters: WRONGTYPE", proclock);
690  LWLockRelease(partitionLock);
691  elog(WARNING, "you don't own a lock of type %s",
692  lockMethodTable->lockModeNames[lockmode]);
693  RemoveLocalLock(locallock);
694  return false;
695  }
696 
697  /*
698  * Do the checking.
699  */
700  if ((lockMethodTable->conflictTab[lockmode] & lock->waitMask) != 0)
701  hasWaiters = true;
702 
703  LWLockRelease(partitionLock);
704 
705  return hasWaiters;
706 }
707 
708 /*
709  * LockAcquire -- Check for lock conflicts, sleep if conflict found,
710  * set lock if/when no conflicts.
711  *
712  * Inputs:
713  * locktag: unique identifier for the lockable object
714  * lockmode: lock mode to acquire
715  * sessionLock: if true, acquire lock for session not current transaction
716  * dontWait: if true, don't wait to acquire lock
717  *
718  * Returns one of:
719  * LOCKACQUIRE_NOT_AVAIL lock not available, and dontWait=true
720  * LOCKACQUIRE_OK lock successfully acquired
721  * LOCKACQUIRE_ALREADY_HELD incremented count for lock already held
722  * LOCKACQUIRE_ALREADY_CLEAR incremented count for lock already clear
723  *
724  * In the normal case where dontWait=false and the caller doesn't need to
725  * distinguish a freshly acquired lock from one already taken earlier in
726  * this same transaction, there is no need to examine the return value.
727  *
728  * Side Effects: The lock is acquired and recorded in lock tables.
729  *
730  * NOTE: if we wait for the lock, there is no way to abort the wait
731  * short of aborting the transaction.
732  */
734 LockAcquire(const LOCKTAG *locktag,
735  LOCKMODE lockmode,
736  bool sessionLock,
737  bool dontWait)
738 {
739  return LockAcquireExtended(locktag, lockmode, sessionLock, dontWait,
740  true, NULL);
741 }
742 
743 /*
744  * LockAcquireExtended - allows us to specify additional options
745  *
746  * reportMemoryError specifies whether a lock request that fills the lock
747  * table should generate an ERROR or not. Passing "false" allows the caller
748  * to attempt to recover from lock-table-full situations, perhaps by forcibly
749  * canceling other lock holders and then retrying. Note, however, that the
750  * return code for that is LOCKACQUIRE_NOT_AVAIL, so that it's unsafe to use
751  * in combination with dontWait = true, as the cause of failure couldn't be
752  * distinguished.
753  *
754  * If locallockp isn't NULL, *locallockp receives a pointer to the LOCALLOCK
755  * table entry if a lock is successfully acquired, or NULL if not.
756  */
759  LOCKMODE lockmode,
760  bool sessionLock,
761  bool dontWait,
762  bool reportMemoryError,
763  LOCALLOCK **locallockp)
764 {
765  LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
766  LockMethod lockMethodTable;
767  LOCALLOCKTAG localtag;
768  LOCALLOCK *locallock;
769  LOCK *lock;
770  PROCLOCK *proclock;
771  bool found;
772  ResourceOwner owner;
773  uint32 hashcode;
774  LWLock *partitionLock;
775  bool found_conflict;
776  bool log_lock = false;
777 
778  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
779  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
780  lockMethodTable = LockMethods[lockmethodid];
781  if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
782  elog(ERROR, "unrecognized lock mode: %d", lockmode);
783 
784  if (RecoveryInProgress() && !InRecovery &&
785  (locktag->locktag_type == LOCKTAG_OBJECT ||
786  locktag->locktag_type == LOCKTAG_RELATION) &&
787  lockmode > RowExclusiveLock)
788  ereport(ERROR,
789  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
790  errmsg("cannot acquire lock mode %s on database objects while recovery is in progress",
791  lockMethodTable->lockModeNames[lockmode]),
792  errhint("Only RowExclusiveLock or less can be acquired on database objects during recovery.")));
793 
794 #ifdef LOCK_DEBUG
795  if (LOCK_DEBUG_ENABLED(locktag))
796  elog(LOG, "LockAcquire: lock [%u,%u] %s",
797  locktag->locktag_field1, locktag->locktag_field2,
798  lockMethodTable->lockModeNames[lockmode]);
799 #endif
800 
801  /* Identify owner for lock */
802  if (sessionLock)
803  owner = NULL;
804  else
805  owner = CurrentResourceOwner;
806 
807  /*
808  * Find or create a LOCALLOCK entry for this lock and lockmode
809  */
810  MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
811  localtag.lock = *locktag;
812  localtag.mode = lockmode;
813 
814  locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
815  &localtag,
816  HASH_ENTER, &found);
817 
818  /*
819  * if it's a new locallock object, initialize it
820  */
821  if (!found)
822  {
823  locallock->lock = NULL;
824  locallock->proclock = NULL;
825  locallock->hashcode = LockTagHashCode(&(localtag.lock));
826  locallock->nLocks = 0;
827  locallock->holdsStrongLockCount = false;
828  locallock->lockCleared = false;
829  locallock->numLockOwners = 0;
830  locallock->maxLockOwners = 8;
831  locallock->lockOwners = NULL; /* in case next line fails */
832  locallock->lockOwners = (LOCALLOCKOWNER *)
834  locallock->maxLockOwners * sizeof(LOCALLOCKOWNER));
835  }
836  else
837  {
838  /* Make sure there will be room to remember the lock */
839  if (locallock->numLockOwners >= locallock->maxLockOwners)
840  {
841  int newsize = locallock->maxLockOwners * 2;
842 
843  locallock->lockOwners = (LOCALLOCKOWNER *)
844  repalloc(locallock->lockOwners,
845  newsize * sizeof(LOCALLOCKOWNER));
846  locallock->maxLockOwners = newsize;
847  }
848  }
849  hashcode = locallock->hashcode;
850 
851  if (locallockp)
852  *locallockp = locallock;
853 
854  /*
855  * If we already hold the lock, we can just increase the count locally.
856  *
857  * If lockCleared is already set, caller need not worry about absorbing
858  * sinval messages related to the lock's object.
859  */
860  if (locallock->nLocks > 0)
861  {
862  GrantLockLocal(locallock, owner);
863  if (locallock->lockCleared)
865  else
867  }
868 
869  /*
870  * We don't acquire any other heavyweight lock while holding the relation
871  * extension lock. We do allow to acquire the same relation extension
872  * lock more than once but that case won't reach here.
873  */
874  Assert(!IsRelationExtensionLockHeld);
875 
876  /*
877  * Prepare to emit a WAL record if acquisition of this lock needs to be
878  * replayed in a standby server.
879  *
880  * Here we prepare to log; after lock is acquired we'll issue log record.
881  * This arrangement simplifies error recovery in case the preparation step
882  * fails.
883  *
884  * Only AccessExclusiveLocks can conflict with lock types that read-only
885  * transactions can acquire in a standby server. Make sure this definition
886  * matches the one in GetRunningTransactionLocks().
887  */
888  if (lockmode >= AccessExclusiveLock &&
889  locktag->locktag_type == LOCKTAG_RELATION &&
890  !RecoveryInProgress() &&
892  {
894  log_lock = true;
895  }
896 
897  /*
898  * Attempt to take lock via fast path, if eligible. But if we remember
899  * having filled up the fast path array, we don't attempt to make any
900  * further use of it until we release some locks. It's possible that some
901  * other backend has transferred some of those locks to the shared hash
902  * table, leaving space free, but it's not worth acquiring the LWLock just
903  * to check. It's also possible that we're acquiring a second or third
904  * lock type on a relation we have already locked using the fast-path, but
905  * for now we don't worry about that case either.
906  */
907  if (EligibleForRelationFastPath(locktag, lockmode) &&
909  {
910  uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
911  bool acquired;
912 
913  /*
914  * LWLockAcquire acts as a memory sequencing point, so it's safe to
915  * assume that any strong locker whose increment to
916  * FastPathStrongRelationLocks->counts becomes visible after we test
917  * it has yet to begin to transfer fast-path locks.
918  */
920  if (FastPathStrongRelationLocks->count[fasthashcode] != 0)
921  acquired = false;
922  else
923  acquired = FastPathGrantRelationLock(locktag->locktag_field2,
924  lockmode);
926  if (acquired)
927  {
928  /*
929  * The locallock might contain stale pointers to some old shared
930  * objects; we MUST reset these to null before considering the
931  * lock to be acquired via fast-path.
932  */
933  locallock->lock = NULL;
934  locallock->proclock = NULL;
935  GrantLockLocal(locallock, owner);
936  return LOCKACQUIRE_OK;
937  }
938  }
939 
940  /*
941  * If this lock could potentially have been taken via the fast-path by
942  * some other backend, we must (temporarily) disable further use of the
943  * fast-path for this lock tag, and migrate any locks already taken via
944  * this method to the main lock table.
945  */
946  if (ConflictsWithRelationFastPath(locktag, lockmode))
947  {
948  uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
949 
950  BeginStrongLockAcquire(locallock, fasthashcode);
951  if (!FastPathTransferRelationLocks(lockMethodTable, locktag,
952  hashcode))
953  {
955  if (locallock->nLocks == 0)
956  RemoveLocalLock(locallock);
957  if (locallockp)
958  *locallockp = NULL;
959  if (reportMemoryError)
960  ereport(ERROR,
961  (errcode(ERRCODE_OUT_OF_MEMORY),
962  errmsg("out of shared memory"),
963  errhint("You might need to increase %s.", "max_locks_per_transaction")));
964  else
965  return LOCKACQUIRE_NOT_AVAIL;
966  }
967  }
968 
969  /*
970  * We didn't find the lock in our LOCALLOCK table, and we didn't manage to
971  * take it via the fast-path, either, so we've got to mess with the shared
972  * lock table.
973  */
974  partitionLock = LockHashPartitionLock(hashcode);
975 
976  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
977 
978  /*
979  * Find or create lock and proclock entries with this tag
980  *
981  * Note: if the locallock object already existed, it might have a pointer
982  * to the lock already ... but we should not assume that that pointer is
983  * valid, since a lock object with zero hold and request counts can go
984  * away anytime. So we have to use SetupLockInTable() to recompute the
985  * lock and proclock pointers, even if they're already set.
986  */
987  proclock = SetupLockInTable(lockMethodTable, MyProc, locktag,
988  hashcode, lockmode);
989  if (!proclock)
990  {
992  LWLockRelease(partitionLock);
993  if (locallock->nLocks == 0)
994  RemoveLocalLock(locallock);
995  if (locallockp)
996  *locallockp = NULL;
997  if (reportMemoryError)
998  ereport(ERROR,
999  (errcode(ERRCODE_OUT_OF_MEMORY),
1000  errmsg("out of shared memory"),
1001  errhint("You might need to increase %s.", "max_locks_per_transaction")));
1002  else
1003  return LOCKACQUIRE_NOT_AVAIL;
1004  }
1005  locallock->proclock = proclock;
1006  lock = proclock->tag.myLock;
1007  locallock->lock = lock;
1008 
1009  /*
1010  * If lock requested conflicts with locks requested by waiters, must join
1011  * wait queue. Otherwise, check for conflict with already-held locks.
1012  * (That's last because most complex check.)
1013  */
1014  if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
1015  found_conflict = true;
1016  else
1017  found_conflict = LockCheckConflicts(lockMethodTable, lockmode,
1018  lock, proclock);
1019 
1020  if (!found_conflict)
1021  {
1022  /* No conflict with held or previously requested locks */
1023  GrantLock(lock, proclock, lockmode);
1024  GrantLockLocal(locallock, owner);
1025  }
1026  else
1027  {
1028  /*
1029  * Set bitmask of locks this process already holds on this object.
1030  */
1031  MyProc->heldLocks = proclock->holdMask;
1032 
1033  /*
1034  * Sleep till someone wakes me up. We do this even in the dontWait
1035  * case, beause while trying to go to sleep, we may discover that we
1036  * can acquire the lock immediately after all.
1037  */
1038 
1039  TRACE_POSTGRESQL_LOCK_WAIT_START(locktag->locktag_field1,
1040  locktag->locktag_field2,
1041  locktag->locktag_field3,
1042  locktag->locktag_field4,
1043  locktag->locktag_type,
1044  lockmode);
1045 
1046  WaitOnLock(locallock, owner, dontWait);
1047 
1048  TRACE_POSTGRESQL_LOCK_WAIT_DONE(locktag->locktag_field1,
1049  locktag->locktag_field2,
1050  locktag->locktag_field3,
1051  locktag->locktag_field4,
1052  locktag->locktag_type,
1053  lockmode);
1054 
1055  /*
1056  * NOTE: do not do any material change of state between here and
1057  * return. All required changes in locktable state must have been
1058  * done when the lock was granted to us --- see notes in WaitOnLock.
1059  */
1060 
1061  /*
1062  * Check the proclock entry status. If dontWait = true, this is an
1063  * expected case; otherwise, it will open happen if something in the
1064  * ipc communication doesn't work correctly.
1065  */
1066  if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
1067  {
1069 
1070  if (dontWait)
1071  {
1072  /*
1073  * We can't acquire the lock immediately. If caller specified
1074  * no blocking, remove useless table entries and return
1075  * LOCKACQUIRE_NOT_AVAIL without waiting.
1076  */
1077  if (proclock->holdMask == 0)
1078  {
1079  uint32 proclock_hashcode;
1080 
1081  proclock_hashcode = ProcLockHashCode(&proclock->tag,
1082  hashcode);
1083  dlist_delete(&proclock->lockLink);
1084  dlist_delete(&proclock->procLink);
1086  &(proclock->tag),
1087  proclock_hashcode,
1088  HASH_REMOVE,
1089  NULL))
1090  elog(PANIC, "proclock table corrupted");
1091  }
1092  else
1093  PROCLOCK_PRINT("LockAcquire: NOWAIT", proclock);
1094  lock->nRequested--;
1095  lock->requested[lockmode]--;
1096  LOCK_PRINT("LockAcquire: conditional lock failed",
1097  lock, lockmode);
1098  Assert((lock->nRequested > 0) &&
1099  (lock->requested[lockmode] >= 0));
1100  Assert(lock->nGranted <= lock->nRequested);
1101  LWLockRelease(partitionLock);
1102  if (locallock->nLocks == 0)
1103  RemoveLocalLock(locallock);
1104  if (locallockp)
1105  *locallockp = NULL;
1106  return LOCKACQUIRE_NOT_AVAIL;
1107  }
1108  else
1109  {
1110  /*
1111  * We should have gotten the lock, but somehow that didn't
1112  * happen. If we get here, it's a bug.
1113  */
1114  PROCLOCK_PRINT("LockAcquire: INCONSISTENT", proclock);
1115  LOCK_PRINT("LockAcquire: INCONSISTENT", lock, lockmode);
1116  LWLockRelease(partitionLock);
1117  elog(ERROR, "LockAcquire failed");
1118  }
1119  }
1120  PROCLOCK_PRINT("LockAcquire: granted", proclock);
1121  LOCK_PRINT("LockAcquire: granted", lock, lockmode);
1122  }
1123 
1124  /*
1125  * Lock state is fully up-to-date now; if we error out after this, no
1126  * special error cleanup is required.
1127  */
1129 
1130  LWLockRelease(partitionLock);
1131 
1132  /*
1133  * Emit a WAL record if acquisition of this lock needs to be replayed in a
1134  * standby server.
1135  */
1136  if (log_lock)
1137  {
1138  /*
1139  * Decode the locktag back to the original values, to avoid sending
1140  * lots of empty bytes with every message. See lock.h to check how a
1141  * locktag is defined for LOCKTAG_RELATION
1142  */
1144  locktag->locktag_field2);
1145  }
1146 
1147  return LOCKACQUIRE_OK;
1148 }
1149 
1150 /*
1151  * Find or create LOCK and PROCLOCK objects as needed for a new lock
1152  * request.
1153  *
1154  * Returns the PROCLOCK object, or NULL if we failed to create the objects
1155  * for lack of shared memory.
1156  *
1157  * The appropriate partition lock must be held at entry, and will be
1158  * held at exit.
1159  */
1160 static PROCLOCK *
1161 SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc,
1162  const LOCKTAG *locktag, uint32 hashcode, LOCKMODE lockmode)
1163 {
1164  LOCK *lock;
1165  PROCLOCK *proclock;
1166  PROCLOCKTAG proclocktag;
1167  uint32 proclock_hashcode;
1168  bool found;
1169 
1170  /*
1171  * Find or create a lock with this tag.
1172  */
1174  locktag,
1175  hashcode,
1177  &found);
1178  if (!lock)
1179  return NULL;
1180 
1181  /*
1182  * if it's a new lock object, initialize it
1183  */
1184  if (!found)
1185  {
1186  lock->grantMask = 0;
1187  lock->waitMask = 0;
1188  dlist_init(&lock->procLocks);
1189  dclist_init(&lock->waitProcs);
1190  lock->nRequested = 0;
1191  lock->nGranted = 0;
1192  MemSet(lock->requested, 0, sizeof(int) * MAX_LOCKMODES);
1193  MemSet(lock->granted, 0, sizeof(int) * MAX_LOCKMODES);
1194  LOCK_PRINT("LockAcquire: new", lock, lockmode);
1195  }
1196  else
1197  {
1198  LOCK_PRINT("LockAcquire: found", lock, lockmode);
1199  Assert((lock->nRequested >= 0) && (lock->requested[lockmode] >= 0));
1200  Assert((lock->nGranted >= 0) && (lock->granted[lockmode] >= 0));
1201  Assert(lock->nGranted <= lock->nRequested);
1202  }
1203 
1204  /*
1205  * Create the hash key for the proclock table.
1206  */
1207  proclocktag.myLock = lock;
1208  proclocktag.myProc = proc;
1209 
1210  proclock_hashcode = ProcLockHashCode(&proclocktag, hashcode);
1211 
1212  /*
1213  * Find or create a proclock entry with this tag
1214  */
1216  &proclocktag,
1217  proclock_hashcode,
1219  &found);
1220  if (!proclock)
1221  {
1222  /* Oops, not enough shmem for the proclock */
1223  if (lock->nRequested == 0)
1224  {
1225  /*
1226  * There are no other requestors of this lock, so garbage-collect
1227  * the lock object. We *must* do this to avoid a permanent leak
1228  * of shared memory, because there won't be anything to cause
1229  * anyone to release the lock object later.
1230  */
1231  Assert(dlist_is_empty(&(lock->procLocks)));
1233  &(lock->tag),
1234  hashcode,
1235  HASH_REMOVE,
1236  NULL))
1237  elog(PANIC, "lock table corrupted");
1238  }
1239  return NULL;
1240  }
1241 
1242  /*
1243  * If new, initialize the new entry
1244  */
1245  if (!found)
1246  {
1247  uint32 partition = LockHashPartition(hashcode);
1248 
1249  /*
1250  * It might seem unsafe to access proclock->groupLeader without a
1251  * lock, but it's not really. Either we are initializing a proclock
1252  * on our own behalf, in which case our group leader isn't changing
1253  * because the group leader for a process can only ever be changed by
1254  * the process itself; or else we are transferring a fast-path lock to
1255  * the main lock table, in which case that process can't change it's
1256  * lock group leader without first releasing all of its locks (and in
1257  * particular the one we are currently transferring).
1258  */
1259  proclock->groupLeader = proc->lockGroupLeader != NULL ?
1260  proc->lockGroupLeader : proc;
1261  proclock->holdMask = 0;
1262  proclock->releaseMask = 0;
1263  /* Add proclock to appropriate lists */
1264  dlist_push_tail(&lock->procLocks, &proclock->lockLink);
1265  dlist_push_tail(&proc->myProcLocks[partition], &proclock->procLink);
1266  PROCLOCK_PRINT("LockAcquire: new", proclock);
1267  }
1268  else
1269  {
1270  PROCLOCK_PRINT("LockAcquire: found", proclock);
1271  Assert((proclock->holdMask & ~lock->grantMask) == 0);
1272 
1273 #ifdef CHECK_DEADLOCK_RISK
1274 
1275  /*
1276  * Issue warning if we already hold a lower-level lock on this object
1277  * and do not hold a lock of the requested level or higher. This
1278  * indicates a deadlock-prone coding practice (eg, we'd have a
1279  * deadlock if another backend were following the same code path at
1280  * about the same time).
1281  *
1282  * This is not enabled by default, because it may generate log entries
1283  * about user-level coding practices that are in fact safe in context.
1284  * It can be enabled to help find system-level problems.
1285  *
1286  * XXX Doing numeric comparison on the lockmodes is a hack; it'd be
1287  * better to use a table. For now, though, this works.
1288  */
1289  {
1290  int i;
1291 
1292  for (i = lockMethodTable->numLockModes; i > 0; i--)
1293  {
1294  if (proclock->holdMask & LOCKBIT_ON(i))
1295  {
1296  if (i >= (int) lockmode)
1297  break; /* safe: we have a lock >= req level */
1298  elog(LOG, "deadlock risk: raising lock level"
1299  " from %s to %s on object %u/%u/%u",
1300  lockMethodTable->lockModeNames[i],
1301  lockMethodTable->lockModeNames[lockmode],
1302  lock->tag.locktag_field1, lock->tag.locktag_field2,
1303  lock->tag.locktag_field3);
1304  break;
1305  }
1306  }
1307  }
1308 #endif /* CHECK_DEADLOCK_RISK */
1309  }
1310 
1311  /*
1312  * lock->nRequested and lock->requested[] count the total number of
1313  * requests, whether granted or waiting, so increment those immediately.
1314  * The other counts don't increment till we get the lock.
1315  */
1316  lock->nRequested++;
1317  lock->requested[lockmode]++;
1318  Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
1319 
1320  /*
1321  * We shouldn't already hold the desired lock; else locallock table is
1322  * broken.
1323  */
1324  if (proclock->holdMask & LOCKBIT_ON(lockmode))
1325  elog(ERROR, "lock %s on object %u/%u/%u is already held",
1326  lockMethodTable->lockModeNames[lockmode],
1327  lock->tag.locktag_field1, lock->tag.locktag_field2,
1328  lock->tag.locktag_field3);
1329 
1330  return proclock;
1331 }
1332 
1333 /*
1334  * Check and set/reset the flag that we hold the relation extension lock.
1335  *
1336  * It is callers responsibility that this function is called after
1337  * acquiring/releasing the relation extension lock.
1338  *
1339  * Pass acquired as true if lock is acquired, false otherwise.
1340  */
1341 static inline void
1342 CheckAndSetLockHeld(LOCALLOCK *locallock, bool acquired)
1343 {
1344 #ifdef USE_ASSERT_CHECKING
1345  if (LOCALLOCK_LOCKTAG(*locallock) == LOCKTAG_RELATION_EXTEND)
1346  IsRelationExtensionLockHeld = acquired;
1347 #endif
1348 }
1349 
1350 /*
1351  * Subroutine to free a locallock entry
1352  */
1353 static void
1355 {
1356  int i;
1357 
1358  for (i = locallock->numLockOwners - 1; i >= 0; i--)
1359  {
1360  if (locallock->lockOwners[i].owner != NULL)
1361  ResourceOwnerForgetLock(locallock->lockOwners[i].owner, locallock);
1362  }
1363  locallock->numLockOwners = 0;
1364  if (locallock->lockOwners != NULL)
1365  pfree(locallock->lockOwners);
1366  locallock->lockOwners = NULL;
1367 
1368  if (locallock->holdsStrongLockCount)
1369  {
1370  uint32 fasthashcode;
1371 
1372  fasthashcode = FastPathStrongLockHashPartition(locallock->hashcode);
1373 
1375  Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
1376  FastPathStrongRelationLocks->count[fasthashcode]--;
1377  locallock->holdsStrongLockCount = false;
1379  }
1380 
1382  &(locallock->tag),
1383  HASH_REMOVE, NULL))
1384  elog(WARNING, "locallock table corrupted");
1385 
1386  /*
1387  * Indicate that the lock is released for certain types of locks
1388  */
1389  CheckAndSetLockHeld(locallock, false);
1390 }
1391 
1392 /*
1393  * LockCheckConflicts -- test whether requested lock conflicts
1394  * with those already granted
1395  *
1396  * Returns true if conflict, false if no conflict.
1397  *
1398  * NOTES:
1399  * Here's what makes this complicated: one process's locks don't
1400  * conflict with one another, no matter what purpose they are held for
1401  * (eg, session and transaction locks do not conflict). Nor do the locks
1402  * of one process in a lock group conflict with those of another process in
1403  * the same group. So, we must subtract off these locks when determining
1404  * whether the requested new lock conflicts with those already held.
1405  */
1406 bool
1408  LOCKMODE lockmode,
1409  LOCK *lock,
1410  PROCLOCK *proclock)
1411 {
1412  int numLockModes = lockMethodTable->numLockModes;
1413  LOCKMASK myLocks;
1414  int conflictMask = lockMethodTable->conflictTab[lockmode];
1415  int conflictsRemaining[MAX_LOCKMODES];
1416  int totalConflictsRemaining = 0;
1417  dlist_iter proclock_iter;
1418  int i;
1419 
1420  /*
1421  * first check for global conflicts: If no locks conflict with my request,
1422  * then I get the lock.
1423  *
1424  * Checking for conflict: lock->grantMask represents the types of
1425  * currently held locks. conflictTable[lockmode] has a bit set for each
1426  * type of lock that conflicts with request. Bitwise compare tells if
1427  * there is a conflict.
1428  */
1429  if (!(conflictMask & lock->grantMask))
1430  {
1431  PROCLOCK_PRINT("LockCheckConflicts: no conflict", proclock);
1432  return false;
1433  }
1434 
1435  /*
1436  * Rats. Something conflicts. But it could still be my own lock, or a
1437  * lock held by another member of my locking group. First, figure out how
1438  * many conflicts remain after subtracting out any locks I hold myself.
1439  */
1440  myLocks = proclock->holdMask;
1441  for (i = 1; i <= numLockModes; i++)
1442  {
1443  if ((conflictMask & LOCKBIT_ON(i)) == 0)
1444  {
1445  conflictsRemaining[i] = 0;
1446  continue;
1447  }
1448  conflictsRemaining[i] = lock->granted[i];
1449  if (myLocks & LOCKBIT_ON(i))
1450  --conflictsRemaining[i];
1451  totalConflictsRemaining += conflictsRemaining[i];
1452  }
1453 
1454  /* If no conflicts remain, we get the lock. */
1455  if (totalConflictsRemaining == 0)
1456  {
1457  PROCLOCK_PRINT("LockCheckConflicts: resolved (simple)", proclock);
1458  return false;
1459  }
1460 
1461  /* If no group locking, it's definitely a conflict. */
1462  if (proclock->groupLeader == MyProc && MyProc->lockGroupLeader == NULL)
1463  {
1464  Assert(proclock->tag.myProc == MyProc);
1465  PROCLOCK_PRINT("LockCheckConflicts: conflicting (simple)",
1466  proclock);
1467  return true;
1468  }
1469 
1470  /*
1471  * The relation extension lock conflict even between the group members.
1472  */
1473  if (LOCK_LOCKTAG(*lock) == LOCKTAG_RELATION_EXTEND)
1474  {
1475  PROCLOCK_PRINT("LockCheckConflicts: conflicting (group)",
1476  proclock);
1477  return true;
1478  }
1479 
1480  /*
1481  * Locks held in conflicting modes by members of our own lock group are
1482  * not real conflicts; we can subtract those out and see if we still have
1483  * a conflict. This is O(N) in the number of processes holding or
1484  * awaiting locks on this object. We could improve that by making the
1485  * shared memory state more complex (and larger) but it doesn't seem worth
1486  * it.
1487  */
1488  dlist_foreach(proclock_iter, &lock->procLocks)
1489  {
1490  PROCLOCK *otherproclock =
1491  dlist_container(PROCLOCK, lockLink, proclock_iter.cur);
1492 
1493  if (proclock != otherproclock &&
1494  proclock->groupLeader == otherproclock->groupLeader &&
1495  (otherproclock->holdMask & conflictMask) != 0)
1496  {
1497  int intersectMask = otherproclock->holdMask & conflictMask;
1498 
1499  for (i = 1; i <= numLockModes; i++)
1500  {
1501  if ((intersectMask & LOCKBIT_ON(i)) != 0)
1502  {
1503  if (conflictsRemaining[i] <= 0)
1504  elog(PANIC, "proclocks held do not match lock");
1505  conflictsRemaining[i]--;
1506  totalConflictsRemaining--;
1507  }
1508  }
1509 
1510  if (totalConflictsRemaining == 0)
1511  {
1512  PROCLOCK_PRINT("LockCheckConflicts: resolved (group)",
1513  proclock);
1514  return false;
1515  }
1516  }
1517  }
1518 
1519  /* Nope, it's a real conflict. */
1520  PROCLOCK_PRINT("LockCheckConflicts: conflicting (group)", proclock);
1521  return true;
1522 }
1523 
1524 /*
1525  * GrantLock -- update the lock and proclock data structures to show
1526  * the lock request has been granted.
1527  *
1528  * NOTE: if proc was blocked, it also needs to be removed from the wait list
1529  * and have its waitLock/waitProcLock fields cleared. That's not done here.
1530  *
1531  * NOTE: the lock grant also has to be recorded in the associated LOCALLOCK
1532  * table entry; but since we may be awaking some other process, we can't do
1533  * that here; it's done by GrantLockLocal, instead.
1534  */
1535 void
1536 GrantLock(LOCK *lock, PROCLOCK *proclock, LOCKMODE lockmode)
1537 {
1538  lock->nGranted++;
1539  lock->granted[lockmode]++;
1540  lock->grantMask |= LOCKBIT_ON(lockmode);
1541  if (lock->granted[lockmode] == lock->requested[lockmode])
1542  lock->waitMask &= LOCKBIT_OFF(lockmode);
1543  proclock->holdMask |= LOCKBIT_ON(lockmode);
1544  LOCK_PRINT("GrantLock", lock, lockmode);
1545  Assert((lock->nGranted > 0) && (lock->granted[lockmode] > 0));
1546  Assert(lock->nGranted <= lock->nRequested);
1547 }
1548 
1549 /*
1550  * UnGrantLock -- opposite of GrantLock.
1551  *
1552  * Updates the lock and proclock data structures to show that the lock
1553  * is no longer held nor requested by the current holder.
1554  *
1555  * Returns true if there were any waiters waiting on the lock that
1556  * should now be woken up with ProcLockWakeup.
1557  */
1558 static bool
1559 UnGrantLock(LOCK *lock, LOCKMODE lockmode,
1560  PROCLOCK *proclock, LockMethod lockMethodTable)
1561 {
1562  bool wakeupNeeded = false;
1563 
1564  Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
1565  Assert((lock->nGranted > 0) && (lock->granted[lockmode] > 0));
1566  Assert(lock->nGranted <= lock->nRequested);
1567 
1568  /*
1569  * fix the general lock stats
1570  */
1571  lock->nRequested--;
1572  lock->requested[lockmode]--;
1573  lock->nGranted--;
1574  lock->granted[lockmode]--;
1575 
1576  if (lock->granted[lockmode] == 0)
1577  {
1578  /* change the conflict mask. No more of this lock type. */
1579  lock->grantMask &= LOCKBIT_OFF(lockmode);
1580  }
1581 
1582  LOCK_PRINT("UnGrantLock: updated", lock, lockmode);
1583 
1584  /*
1585  * We need only run ProcLockWakeup if the released lock conflicts with at
1586  * least one of the lock types requested by waiter(s). Otherwise whatever
1587  * conflict made them wait must still exist. NOTE: before MVCC, we could
1588  * skip wakeup if lock->granted[lockmode] was still positive. But that's
1589  * not true anymore, because the remaining granted locks might belong to
1590  * some waiter, who could now be awakened because he doesn't conflict with
1591  * his own locks.
1592  */
1593  if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
1594  wakeupNeeded = true;
1595 
1596  /*
1597  * Now fix the per-proclock state.
1598  */
1599  proclock->holdMask &= LOCKBIT_OFF(lockmode);
1600  PROCLOCK_PRINT("UnGrantLock: updated", proclock);
1601 
1602  return wakeupNeeded;
1603 }
1604 
1605 /*
1606  * CleanUpLock -- clean up after releasing a lock. We garbage-collect the
1607  * proclock and lock objects if possible, and call ProcLockWakeup if there
1608  * are remaining requests and the caller says it's OK. (Normally, this
1609  * should be called after UnGrantLock, and wakeupNeeded is the result from
1610  * UnGrantLock.)
1611  *
1612  * The appropriate partition lock must be held at entry, and will be
1613  * held at exit.
1614  */
1615 static void
1616 CleanUpLock(LOCK *lock, PROCLOCK *proclock,
1617  LockMethod lockMethodTable, uint32 hashcode,
1618  bool wakeupNeeded)
1619 {
1620  /*
1621  * If this was my last hold on this lock, delete my entry in the proclock
1622  * table.
1623  */
1624  if (proclock->holdMask == 0)
1625  {
1626  uint32 proclock_hashcode;
1627 
1628  PROCLOCK_PRINT("CleanUpLock: deleting", proclock);
1629  dlist_delete(&proclock->lockLink);
1630  dlist_delete(&proclock->procLink);
1631  proclock_hashcode = ProcLockHashCode(&proclock->tag, hashcode);
1633  &(proclock->tag),
1634  proclock_hashcode,
1635  HASH_REMOVE,
1636  NULL))
1637  elog(PANIC, "proclock table corrupted");
1638  }
1639 
1640  if (lock->nRequested == 0)
1641  {
1642  /*
1643  * The caller just released the last lock, so garbage-collect the lock
1644  * object.
1645  */
1646  LOCK_PRINT("CleanUpLock: deleting", lock, 0);
1647  Assert(dlist_is_empty(&lock->procLocks));
1649  &(lock->tag),
1650  hashcode,
1651  HASH_REMOVE,
1652  NULL))
1653  elog(PANIC, "lock table corrupted");
1654  }
1655  else if (wakeupNeeded)
1656  {
1657  /* There are waiters on this lock, so wake them up. */
1658  ProcLockWakeup(lockMethodTable, lock);
1659  }
1660 }
1661 
1662 /*
1663  * GrantLockLocal -- update the locallock data structures to show
1664  * the lock request has been granted.
1665  *
1666  * We expect that LockAcquire made sure there is room to add a new
1667  * ResourceOwner entry.
1668  */
1669 static void
1671 {
1672  LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
1673  int i;
1674 
1675  Assert(locallock->numLockOwners < locallock->maxLockOwners);
1676  /* Count the total */
1677  locallock->nLocks++;
1678  /* Count the per-owner lock */
1679  for (i = 0; i < locallock->numLockOwners; i++)
1680  {
1681  if (lockOwners[i].owner == owner)
1682  {
1683  lockOwners[i].nLocks++;
1684  return;
1685  }
1686  }
1687  lockOwners[i].owner = owner;
1688  lockOwners[i].nLocks = 1;
1689  locallock->numLockOwners++;
1690  if (owner != NULL)
1691  ResourceOwnerRememberLock(owner, locallock);
1692 
1693  /* Indicate that the lock is acquired for certain types of locks. */
1694  CheckAndSetLockHeld(locallock, true);
1695 }
1696 
1697 /*
1698  * BeginStrongLockAcquire - inhibit use of fastpath for a given LOCALLOCK,
1699  * and arrange for error cleanup if it fails
1700  */
1701 static void
1702 BeginStrongLockAcquire(LOCALLOCK *locallock, uint32 fasthashcode)
1703 {
1704  Assert(StrongLockInProgress == NULL);
1705  Assert(locallock->holdsStrongLockCount == false);
1706 
1707  /*
1708  * Adding to a memory location is not atomic, so we take a spinlock to
1709  * ensure we don't collide with someone else trying to bump the count at
1710  * the same time.
1711  *
1712  * XXX: It might be worth considering using an atomic fetch-and-add
1713  * instruction here, on architectures where that is supported.
1714  */
1715 
1717  FastPathStrongRelationLocks->count[fasthashcode]++;
1718  locallock->holdsStrongLockCount = true;
1719  StrongLockInProgress = locallock;
1721 }
1722 
1723 /*
1724  * FinishStrongLockAcquire - cancel pending cleanup for a strong lock
1725  * acquisition once it's no longer needed
1726  */
1727 static void
1729 {
1730  StrongLockInProgress = NULL;
1731 }
1732 
1733 /*
1734  * AbortStrongLockAcquire - undo strong lock state changes performed by
1735  * BeginStrongLockAcquire.
1736  */
1737 void
1739 {
1740  uint32 fasthashcode;
1741  LOCALLOCK *locallock = StrongLockInProgress;
1742 
1743  if (locallock == NULL)
1744  return;
1745 
1746  fasthashcode = FastPathStrongLockHashPartition(locallock->hashcode);
1747  Assert(locallock->holdsStrongLockCount == true);
1749  Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
1750  FastPathStrongRelationLocks->count[fasthashcode]--;
1751  locallock->holdsStrongLockCount = false;
1752  StrongLockInProgress = NULL;
1754 }
1755 
1756 /*
1757  * GrantAwaitedLock -- call GrantLockLocal for the lock we are doing
1758  * WaitOnLock on.
1759  *
1760  * proc.c needs this for the case where we are booted off the lock by
1761  * timeout, but discover that someone granted us the lock anyway.
1762  *
1763  * We could just export GrantLockLocal, but that would require including
1764  * resowner.h in lock.h, which creates circularity.
1765  */
1766 void
1768 {
1770 }
1771 
1772 /*
1773  * MarkLockClear -- mark an acquired lock as "clear"
1774  *
1775  * This means that we know we have absorbed all sinval messages that other
1776  * sessions generated before we acquired this lock, and so we can confidently
1777  * assume we know about any catalog changes protected by this lock.
1778  */
1779 void
1781 {
1782  Assert(locallock->nLocks > 0);
1783  locallock->lockCleared = true;
1784 }
1785 
1786 /*
1787  * WaitOnLock -- wait to acquire a lock
1788  *
1789  * Caller must have set MyProc->heldLocks to reflect locks already held
1790  * on the lockable object by this process.
1791  *
1792  * The appropriate partition lock must be held at entry, and will still be
1793  * held at exit.
1794  */
1795 static void
1796 WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner, bool dontWait)
1797 {
1798  LOCKMETHODID lockmethodid = LOCALLOCK_LOCKMETHOD(*locallock);
1799  LockMethod lockMethodTable = LockMethods[lockmethodid];
1800 
1801  LOCK_PRINT("WaitOnLock: sleeping on lock",
1802  locallock->lock, locallock->tag.mode);
1803 
1804  /* adjust the process title to indicate that it's waiting */
1805  set_ps_display_suffix("waiting");
1806 
1807  awaitedLock = locallock;
1808  awaitedOwner = owner;
1809 
1810  /*
1811  * NOTE: Think not to put any shared-state cleanup after the call to
1812  * ProcSleep, in either the normal or failure path. The lock state must
1813  * be fully set by the lock grantor, or by CheckDeadLock if we give up
1814  * waiting for the lock. This is necessary because of the possibility
1815  * that a cancel/die interrupt will interrupt ProcSleep after someone else
1816  * grants us the lock, but before we've noticed it. Hence, after granting,
1817  * the locktable state must fully reflect the fact that we own the lock;
1818  * we can't do additional work on return.
1819  *
1820  * We can and do use a PG_TRY block to try to clean up after failure, but
1821  * this still has a major limitation: elog(FATAL) can occur while waiting
1822  * (eg, a "die" interrupt), and then control won't come back here. So all
1823  * cleanup of essential state should happen in LockErrorCleanup, not here.
1824  * We can use PG_TRY to clear the "waiting" status flags, since doing that
1825  * is unimportant if the process exits.
1826  */
1827  PG_TRY();
1828  {
1829  /*
1830  * If dontWait = true, we handle success and failure in the same way
1831  * here. The caller will be able to sort out what has happened.
1832  */
1833  if (ProcSleep(locallock, lockMethodTable, dontWait) != PROC_WAIT_STATUS_OK
1834  && !dontWait)
1835  {
1836 
1837  /*
1838  * We failed as a result of a deadlock, see CheckDeadLock(). Quit
1839  * now.
1840  */
1841  awaitedLock = NULL;
1842  LOCK_PRINT("WaitOnLock: aborting on lock",
1843  locallock->lock, locallock->tag.mode);
1845 
1846  /*
1847  * Now that we aren't holding the partition lock, we can give an
1848  * error report including details about the detected deadlock.
1849  */
1850  DeadLockReport();
1851  /* not reached */
1852  }
1853  }
1854  PG_CATCH();
1855  {
1856  /* In this path, awaitedLock remains set until LockErrorCleanup */
1857 
1858  /* reset ps display to remove the suffix */
1860 
1861  /* and propagate the error */
1862  PG_RE_THROW();
1863  }
1864  PG_END_TRY();
1865 
1866  awaitedLock = NULL;
1867 
1868  /* reset ps display to remove the suffix */
1870 
1871  LOCK_PRINT("WaitOnLock: wakeup on lock",
1872  locallock->lock, locallock->tag.mode);
1873 }
1874 
1875 /*
1876  * Remove a proc from the wait-queue it is on (caller must know it is on one).
1877  * This is only used when the proc has failed to get the lock, so we set its
1878  * waitStatus to PROC_WAIT_STATUS_ERROR.
1879  *
1880  * Appropriate partition lock must be held by caller. Also, caller is
1881  * responsible for signaling the proc if needed.
1882  *
1883  * NB: this does not clean up any locallock object that may exist for the lock.
1884  */
1885 void
1887 {
1888  LOCK *waitLock = proc->waitLock;
1889  PROCLOCK *proclock = proc->waitProcLock;
1890  LOCKMODE lockmode = proc->waitLockMode;
1891  LOCKMETHODID lockmethodid = LOCK_LOCKMETHOD(*waitLock);
1892 
1893  /* Make sure proc is waiting */
1895  Assert(proc->links.next != NULL);
1896  Assert(waitLock);
1897  Assert(!dclist_is_empty(&waitLock->waitProcs));
1898  Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
1899 
1900  /* Remove proc from lock's wait queue */
1901  dclist_delete_from_thoroughly(&waitLock->waitProcs, &proc->links);
1902 
1903  /* Undo increments of request counts by waiting process */
1904  Assert(waitLock->nRequested > 0);
1905  Assert(waitLock->nRequested > proc->waitLock->nGranted);
1906  waitLock->nRequested--;
1907  Assert(waitLock->requested[lockmode] > 0);
1908  waitLock->requested[lockmode]--;
1909  /* don't forget to clear waitMask bit if appropriate */
1910  if (waitLock->granted[lockmode] == waitLock->requested[lockmode])
1911  waitLock->waitMask &= LOCKBIT_OFF(lockmode);
1912 
1913  /* Clean up the proc's own state, and pass it the ok/fail signal */
1914  proc->waitLock = NULL;
1915  proc->waitProcLock = NULL;
1917 
1918  /*
1919  * Delete the proclock immediately if it represents no already-held locks.
1920  * (This must happen now because if the owner of the lock decides to
1921  * release it, and the requested/granted counts then go to zero,
1922  * LockRelease expects there to be no remaining proclocks.) Then see if
1923  * any other waiters for the lock can be woken up now.
1924  */
1925  CleanUpLock(waitLock, proclock,
1926  LockMethods[lockmethodid], hashcode,
1927  true);
1928 }
1929 
1930 /*
1931  * LockRelease -- look up 'locktag' and release one 'lockmode' lock on it.
1932  * Release a session lock if 'sessionLock' is true, else release a
1933  * regular transaction lock.
1934  *
1935  * Side Effects: find any waiting processes that are now wakable,
1936  * grant them their requested locks and awaken them.
1937  * (We have to grant the lock here to avoid a race between
1938  * the waking process and any new process to
1939  * come along and request the lock.)
1940  */
1941 bool
1942 LockRelease(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock)
1943 {
1944  LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
1945  LockMethod lockMethodTable;
1946  LOCALLOCKTAG localtag;
1947  LOCALLOCK *locallock;
1948  LOCK *lock;
1949  PROCLOCK *proclock;
1950  LWLock *partitionLock;
1951  bool wakeupNeeded;
1952 
1953  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
1954  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
1955  lockMethodTable = LockMethods[lockmethodid];
1956  if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
1957  elog(ERROR, "unrecognized lock mode: %d", lockmode);
1958 
1959 #ifdef LOCK_DEBUG
1960  if (LOCK_DEBUG_ENABLED(locktag))
1961  elog(LOG, "LockRelease: lock [%u,%u] %s",
1962  locktag->locktag_field1, locktag->locktag_field2,
1963  lockMethodTable->lockModeNames[lockmode]);
1964 #endif
1965 
1966  /*
1967  * Find the LOCALLOCK entry for this lock and lockmode
1968  */
1969  MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
1970  localtag.lock = *locktag;
1971  localtag.mode = lockmode;
1972 
1973  locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
1974  &localtag,
1975  HASH_FIND, NULL);
1976 
1977  /*
1978  * let the caller print its own error message, too. Do not ereport(ERROR).
1979  */
1980  if (!locallock || locallock->nLocks <= 0)
1981  {
1982  elog(WARNING, "you don't own a lock of type %s",
1983  lockMethodTable->lockModeNames[lockmode]);
1984  return false;
1985  }
1986 
1987  /*
1988  * Decrease the count for the resource owner.
1989  */
1990  {
1991  LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
1992  ResourceOwner owner;
1993  int i;
1994 
1995  /* Identify owner for lock */
1996  if (sessionLock)
1997  owner = NULL;
1998  else
1999  owner = CurrentResourceOwner;
2000 
2001  for (i = locallock->numLockOwners - 1; i >= 0; i--)
2002  {
2003  if (lockOwners[i].owner == owner)
2004  {
2005  Assert(lockOwners[i].nLocks > 0);
2006  if (--lockOwners[i].nLocks == 0)
2007  {
2008  if (owner != NULL)
2009  ResourceOwnerForgetLock(owner, locallock);
2010  /* compact out unused slot */
2011  locallock->numLockOwners--;
2012  if (i < locallock->numLockOwners)
2013  lockOwners[i] = lockOwners[locallock->numLockOwners];
2014  }
2015  break;
2016  }
2017  }
2018  if (i < 0)
2019  {
2020  /* don't release a lock belonging to another owner */
2021  elog(WARNING, "you don't own a lock of type %s",
2022  lockMethodTable->lockModeNames[lockmode]);
2023  return false;
2024  }
2025  }
2026 
2027  /*
2028  * Decrease the total local count. If we're still holding the lock, we're
2029  * done.
2030  */
2031  locallock->nLocks--;
2032 
2033  if (locallock->nLocks > 0)
2034  return true;
2035 
2036  /*
2037  * At this point we can no longer suppose we are clear of invalidation
2038  * messages related to this lock. Although we'll delete the LOCALLOCK
2039  * object before any intentional return from this routine, it seems worth
2040  * the trouble to explicitly reset lockCleared right now, just in case
2041  * some error prevents us from deleting the LOCALLOCK.
2042  */
2043  locallock->lockCleared = false;
2044 
2045  /* Attempt fast release of any lock eligible for the fast path. */
2046  if (EligibleForRelationFastPath(locktag, lockmode) &&
2048  {
2049  bool released;
2050 
2051  /*
2052  * We might not find the lock here, even if we originally entered it
2053  * here. Another backend may have moved it to the main table.
2054  */
2056  released = FastPathUnGrantRelationLock(locktag->locktag_field2,
2057  lockmode);
2059  if (released)
2060  {
2061  RemoveLocalLock(locallock);
2062  return true;
2063  }
2064  }
2065 
2066  /*
2067  * Otherwise we've got to mess with the shared lock table.
2068  */
2069  partitionLock = LockHashPartitionLock(locallock->hashcode);
2070 
2071  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
2072 
2073  /*
2074  * Normally, we don't need to re-find the lock or proclock, since we kept
2075  * their addresses in the locallock table, and they couldn't have been
2076  * removed while we were holding a lock on them. But it's possible that
2077  * the lock was taken fast-path and has since been moved to the main hash
2078  * table by another backend, in which case we will need to look up the
2079  * objects here. We assume the lock field is NULL if so.
2080  */
2081  lock = locallock->lock;
2082  if (!lock)
2083  {
2084  PROCLOCKTAG proclocktag;
2085 
2086  Assert(EligibleForRelationFastPath(locktag, lockmode));
2088  locktag,
2089  locallock->hashcode,
2090  HASH_FIND,
2091  NULL);
2092  if (!lock)
2093  elog(ERROR, "failed to re-find shared lock object");
2094  locallock->lock = lock;
2095 
2096  proclocktag.myLock = lock;
2097  proclocktag.myProc = MyProc;
2099  &proclocktag,
2100  HASH_FIND,
2101  NULL);
2102  if (!locallock->proclock)
2103  elog(ERROR, "failed to re-find shared proclock object");
2104  }
2105  LOCK_PRINT("LockRelease: found", lock, lockmode);
2106  proclock = locallock->proclock;
2107  PROCLOCK_PRINT("LockRelease: found", proclock);
2108 
2109  /*
2110  * Double-check that we are actually holding a lock of the type we want to
2111  * release.
2112  */
2113  if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
2114  {
2115  PROCLOCK_PRINT("LockRelease: WRONGTYPE", proclock);
2116  LWLockRelease(partitionLock);
2117  elog(WARNING, "you don't own a lock of type %s",
2118  lockMethodTable->lockModeNames[lockmode]);
2119  RemoveLocalLock(locallock);
2120  return false;
2121  }
2122 
2123  /*
2124  * Do the releasing. CleanUpLock will waken any now-wakable waiters.
2125  */
2126  wakeupNeeded = UnGrantLock(lock, lockmode, proclock, lockMethodTable);
2127 
2128  CleanUpLock(lock, proclock,
2129  lockMethodTable, locallock->hashcode,
2130  wakeupNeeded);
2131 
2132  LWLockRelease(partitionLock);
2133 
2134  RemoveLocalLock(locallock);
2135  return true;
2136 }
2137 
2138 /*
2139  * LockReleaseAll -- Release all locks of the specified lock method that
2140  * are held by the current process.
2141  *
2142  * Well, not necessarily *all* locks. The available behaviors are:
2143  * allLocks == true: release all locks including session locks.
2144  * allLocks == false: release all non-session locks.
2145  */
2146 void
2147 LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks)
2148 {
2149  HASH_SEQ_STATUS status;
2150  LockMethod lockMethodTable;
2151  int i,
2152  numLockModes;
2153  LOCALLOCK *locallock;
2154  LOCK *lock;
2155  int partition;
2156  bool have_fast_path_lwlock = false;
2157 
2158  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
2159  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
2160  lockMethodTable = LockMethods[lockmethodid];
2161 
2162 #ifdef LOCK_DEBUG
2163  if (*(lockMethodTable->trace_flag))
2164  elog(LOG, "LockReleaseAll: lockmethod=%d", lockmethodid);
2165 #endif
2166 
2167  /*
2168  * Get rid of our fast-path VXID lock, if appropriate. Note that this is
2169  * the only way that the lock we hold on our own VXID can ever get
2170  * released: it is always and only released when a toplevel transaction
2171  * ends.
2172  */
2173  if (lockmethodid == DEFAULT_LOCKMETHOD)
2175 
2176  numLockModes = lockMethodTable->numLockModes;
2177 
2178  /*
2179  * First we run through the locallock table and get rid of unwanted
2180  * entries, then we scan the process's proclocks and get rid of those. We
2181  * do this separately because we may have multiple locallock entries
2182  * pointing to the same proclock, and we daren't end up with any dangling
2183  * pointers. Fast-path locks are cleaned up during the locallock table
2184  * scan, though.
2185  */
2187 
2188  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
2189  {
2190  /*
2191  * If the LOCALLOCK entry is unused, we must've run out of shared
2192  * memory while trying to set up this lock. Just forget the local
2193  * entry.
2194  */
2195  if (locallock->nLocks == 0)
2196  {
2197  RemoveLocalLock(locallock);
2198  continue;
2199  }
2200 
2201  /* Ignore items that are not of the lockmethod to be removed */
2202  if (LOCALLOCK_LOCKMETHOD(*locallock) != lockmethodid)
2203  continue;
2204 
2205  /*
2206  * If we are asked to release all locks, we can just zap the entry.
2207  * Otherwise, must scan to see if there are session locks. We assume
2208  * there is at most one lockOwners entry for session locks.
2209  */
2210  if (!allLocks)
2211  {
2212  LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
2213 
2214  /* If session lock is above array position 0, move it down to 0 */
2215  for (i = 0; i < locallock->numLockOwners; i++)
2216  {
2217  if (lockOwners[i].owner == NULL)
2218  lockOwners[0] = lockOwners[i];
2219  else
2220  ResourceOwnerForgetLock(lockOwners[i].owner, locallock);
2221  }
2222 
2223  if (locallock->numLockOwners > 0 &&
2224  lockOwners[0].owner == NULL &&
2225  lockOwners[0].nLocks > 0)
2226  {
2227  /* Fix the locallock to show just the session locks */
2228  locallock->nLocks = lockOwners[0].nLocks;
2229  locallock->numLockOwners = 1;
2230  /* We aren't deleting this locallock, so done */
2231  continue;
2232  }
2233  else
2234  locallock->numLockOwners = 0;
2235  }
2236 
2237  /*
2238  * If the lock or proclock pointers are NULL, this lock was taken via
2239  * the relation fast-path (and is not known to have been transferred).
2240  */
2241  if (locallock->proclock == NULL || locallock->lock == NULL)
2242  {
2243  LOCKMODE lockmode = locallock->tag.mode;
2244  Oid relid;
2245 
2246  /* Verify that a fast-path lock is what we've got. */
2247  if (!EligibleForRelationFastPath(&locallock->tag.lock, lockmode))
2248  elog(PANIC, "locallock table corrupted");
2249 
2250  /*
2251  * If we don't currently hold the LWLock that protects our
2252  * fast-path data structures, we must acquire it before attempting
2253  * to release the lock via the fast-path. We will continue to
2254  * hold the LWLock until we're done scanning the locallock table,
2255  * unless we hit a transferred fast-path lock. (XXX is this
2256  * really such a good idea? There could be a lot of entries ...)
2257  */
2258  if (!have_fast_path_lwlock)
2259  {
2261  have_fast_path_lwlock = true;
2262  }
2263 
2264  /* Attempt fast-path release. */
2265  relid = locallock->tag.lock.locktag_field2;
2266  if (FastPathUnGrantRelationLock(relid, lockmode))
2267  {
2268  RemoveLocalLock(locallock);
2269  continue;
2270  }
2271 
2272  /*
2273  * Our lock, originally taken via the fast path, has been
2274  * transferred to the main lock table. That's going to require
2275  * some extra work, so release our fast-path lock before starting.
2276  */
2278  have_fast_path_lwlock = false;
2279 
2280  /*
2281  * Now dump the lock. We haven't got a pointer to the LOCK or
2282  * PROCLOCK in this case, so we have to handle this a bit
2283  * differently than a normal lock release. Unfortunately, this
2284  * requires an extra LWLock acquire-and-release cycle on the
2285  * partitionLock, but hopefully it shouldn't happen often.
2286  */
2287  LockRefindAndRelease(lockMethodTable, MyProc,
2288  &locallock->tag.lock, lockmode, false);
2289  RemoveLocalLock(locallock);
2290  continue;
2291  }
2292 
2293  /* Mark the proclock to show we need to release this lockmode */
2294  if (locallock->nLocks > 0)
2295  locallock->proclock->releaseMask |= LOCKBIT_ON(locallock->tag.mode);
2296 
2297  /* And remove the locallock hashtable entry */
2298  RemoveLocalLock(locallock);
2299  }
2300 
2301  /* Done with the fast-path data structures */
2302  if (have_fast_path_lwlock)
2304 
2305  /*
2306  * Now, scan each lock partition separately.
2307  */
2308  for (partition = 0; partition < NUM_LOCK_PARTITIONS; partition++)
2309  {
2310  LWLock *partitionLock;
2311  dlist_head *procLocks = &MyProc->myProcLocks[partition];
2312  dlist_mutable_iter proclock_iter;
2313 
2314  partitionLock = LockHashPartitionLockByIndex(partition);
2315 
2316  /*
2317  * If the proclock list for this partition is empty, we can skip
2318  * acquiring the partition lock. This optimization is trickier than
2319  * it looks, because another backend could be in process of adding
2320  * something to our proclock list due to promoting one of our
2321  * fast-path locks. However, any such lock must be one that we
2322  * decided not to delete above, so it's okay to skip it again now;
2323  * we'd just decide not to delete it again. We must, however, be
2324  * careful to re-fetch the list header once we've acquired the
2325  * partition lock, to be sure we have a valid, up-to-date pointer.
2326  * (There is probably no significant risk if pointer fetch/store is
2327  * atomic, but we don't wish to assume that.)
2328  *
2329  * XXX This argument assumes that the locallock table correctly
2330  * represents all of our fast-path locks. While allLocks mode
2331  * guarantees to clean up all of our normal locks regardless of the
2332  * locallock situation, we lose that guarantee for fast-path locks.
2333  * This is not ideal.
2334  */
2335  if (dlist_is_empty(procLocks))
2336  continue; /* needn't examine this partition */
2337 
2338  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
2339 
2340  dlist_foreach_modify(proclock_iter, procLocks)
2341  {
2342  PROCLOCK *proclock = dlist_container(PROCLOCK, procLink, proclock_iter.cur);
2343  bool wakeupNeeded = false;
2344 
2345  Assert(proclock->tag.myProc == MyProc);
2346 
2347  lock = proclock->tag.myLock;
2348 
2349  /* Ignore items that are not of the lockmethod to be removed */
2350  if (LOCK_LOCKMETHOD(*lock) != lockmethodid)
2351  continue;
2352 
2353  /*
2354  * In allLocks mode, force release of all locks even if locallock
2355  * table had problems
2356  */
2357  if (allLocks)
2358  proclock->releaseMask = proclock->holdMask;
2359  else
2360  Assert((proclock->releaseMask & ~proclock->holdMask) == 0);
2361 
2362  /*
2363  * Ignore items that have nothing to be released, unless they have
2364  * holdMask == 0 and are therefore recyclable
2365  */
2366  if (proclock->releaseMask == 0 && proclock->holdMask != 0)
2367  continue;
2368 
2369  PROCLOCK_PRINT("LockReleaseAll", proclock);
2370  LOCK_PRINT("LockReleaseAll", lock, 0);
2371  Assert(lock->nRequested >= 0);
2372  Assert(lock->nGranted >= 0);
2373  Assert(lock->nGranted <= lock->nRequested);
2374  Assert((proclock->holdMask & ~lock->grantMask) == 0);
2375 
2376  /*
2377  * Release the previously-marked lock modes
2378  */
2379  for (i = 1; i <= numLockModes; i++)
2380  {
2381  if (proclock->releaseMask & LOCKBIT_ON(i))
2382  wakeupNeeded |= UnGrantLock(lock, i, proclock,
2383  lockMethodTable);
2384  }
2385  Assert((lock->nRequested >= 0) && (lock->nGranted >= 0));
2386  Assert(lock->nGranted <= lock->nRequested);
2387  LOCK_PRINT("LockReleaseAll: updated", lock, 0);
2388 
2389  proclock->releaseMask = 0;
2390 
2391  /* CleanUpLock will wake up waiters if needed. */
2392  CleanUpLock(lock, proclock,
2393  lockMethodTable,
2394  LockTagHashCode(&lock->tag),
2395  wakeupNeeded);
2396  } /* loop over PROCLOCKs within this partition */
2397 
2398  LWLockRelease(partitionLock);
2399  } /* loop over partitions */
2400 
2401 #ifdef LOCK_DEBUG
2402  if (*(lockMethodTable->trace_flag))
2403  elog(LOG, "LockReleaseAll done");
2404 #endif
2405 }
2406 
2407 /*
2408  * LockReleaseSession -- Release all session locks of the specified lock method
2409  * that are held by the current process.
2410  */
2411 void
2413 {
2414  HASH_SEQ_STATUS status;
2415  LOCALLOCK *locallock;
2416 
2417  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
2418  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
2419 
2421 
2422  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
2423  {
2424  /* Ignore items that are not of the specified lock method */
2425  if (LOCALLOCK_LOCKMETHOD(*locallock) != lockmethodid)
2426  continue;
2427 
2428  ReleaseLockIfHeld(locallock, true);
2429  }
2430 }
2431 
2432 /*
2433  * LockReleaseCurrentOwner
2434  * Release all locks belonging to CurrentResourceOwner
2435  *
2436  * If the caller knows what those locks are, it can pass them as an array.
2437  * That speeds up the call significantly, when a lot of locks are held.
2438  * Otherwise, pass NULL for locallocks, and we'll traverse through our hash
2439  * table to find them.
2440  */
2441 void
2442 LockReleaseCurrentOwner(LOCALLOCK **locallocks, int nlocks)
2443 {
2444  if (locallocks == NULL)
2445  {
2446  HASH_SEQ_STATUS status;
2447  LOCALLOCK *locallock;
2448 
2450 
2451  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
2452  ReleaseLockIfHeld(locallock, false);
2453  }
2454  else
2455  {
2456  int i;
2457 
2458  for (i = nlocks - 1; i >= 0; i--)
2459  ReleaseLockIfHeld(locallocks[i], false);
2460  }
2461 }
2462 
2463 /*
2464  * ReleaseLockIfHeld
2465  * Release any session-level locks on this lockable object if sessionLock
2466  * is true; else, release any locks held by CurrentResourceOwner.
2467  *
2468  * It is tempting to pass this a ResourceOwner pointer (or NULL for session
2469  * locks), but without refactoring LockRelease() we cannot support releasing
2470  * locks belonging to resource owners other than CurrentResourceOwner.
2471  * If we were to refactor, it'd be a good idea to fix it so we don't have to
2472  * do a hashtable lookup of the locallock, too. However, currently this
2473  * function isn't used heavily enough to justify refactoring for its
2474  * convenience.
2475  */
2476 static void
2477 ReleaseLockIfHeld(LOCALLOCK *locallock, bool sessionLock)
2478 {
2479  ResourceOwner owner;
2480  LOCALLOCKOWNER *lockOwners;
2481  int i;
2482 
2483  /* Identify owner for lock (must match LockRelease!) */
2484  if (sessionLock)
2485  owner = NULL;
2486  else
2487  owner = CurrentResourceOwner;
2488 
2489  /* Scan to see if there are any locks belonging to the target owner */
2490  lockOwners = locallock->lockOwners;
2491  for (i = locallock->numLockOwners - 1; i >= 0; i--)
2492  {
2493  if (lockOwners[i].owner == owner)
2494  {
2495  Assert(lockOwners[i].nLocks > 0);
2496  if (lockOwners[i].nLocks < locallock->nLocks)
2497  {
2498  /*
2499  * We will still hold this lock after forgetting this
2500  * ResourceOwner.
2501  */
2502  locallock->nLocks -= lockOwners[i].nLocks;
2503  /* compact out unused slot */
2504  locallock->numLockOwners--;
2505  if (owner != NULL)
2506  ResourceOwnerForgetLock(owner, locallock);
2507  if (i < locallock->numLockOwners)
2508  lockOwners[i] = lockOwners[locallock->numLockOwners];
2509  }
2510  else
2511  {
2512  Assert(lockOwners[i].nLocks == locallock->nLocks);
2513  /* We want to call LockRelease just once */
2514  lockOwners[i].nLocks = 1;
2515  locallock->nLocks = 1;
2516  if (!LockRelease(&locallock->tag.lock,
2517  locallock->tag.mode,
2518  sessionLock))
2519  elog(WARNING, "ReleaseLockIfHeld: failed??");
2520  }
2521  break;
2522  }
2523  }
2524 }
2525 
2526 /*
2527  * LockReassignCurrentOwner
2528  * Reassign all locks belonging to CurrentResourceOwner to belong
2529  * to its parent resource owner.
2530  *
2531  * If the caller knows what those locks are, it can pass them as an array.
2532  * That speeds up the call significantly, when a lot of locks are held
2533  * (e.g pg_dump with a large schema). Otherwise, pass NULL for locallocks,
2534  * and we'll traverse through our hash table to find them.
2535  */
2536 void
2537 LockReassignCurrentOwner(LOCALLOCK **locallocks, int nlocks)
2538 {
2540 
2541  Assert(parent != NULL);
2542 
2543  if (locallocks == NULL)
2544  {
2545  HASH_SEQ_STATUS status;
2546  LOCALLOCK *locallock;
2547 
2549 
2550  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
2551  LockReassignOwner(locallock, parent);
2552  }
2553  else
2554  {
2555  int i;
2556 
2557  for (i = nlocks - 1; i >= 0; i--)
2558  LockReassignOwner(locallocks[i], parent);
2559  }
2560 }
2561 
2562 /*
2563  * Subroutine of LockReassignCurrentOwner. Reassigns a given lock belonging to
2564  * CurrentResourceOwner to its parent.
2565  */
2566 static void
2568 {
2569  LOCALLOCKOWNER *lockOwners;
2570  int i;
2571  int ic = -1;
2572  int ip = -1;
2573 
2574  /*
2575  * Scan to see if there are any locks belonging to current owner or its
2576  * parent
2577  */
2578  lockOwners = locallock->lockOwners;
2579  for (i = locallock->numLockOwners - 1; i >= 0; i--)
2580  {
2581  if (lockOwners[i].owner == CurrentResourceOwner)
2582  ic = i;
2583  else if (lockOwners[i].owner == parent)
2584  ip = i;
2585  }
2586 
2587  if (ic < 0)
2588  return; /* no current locks */
2589 
2590  if (ip < 0)
2591  {
2592  /* Parent has no slot, so just give it the child's slot */
2593  lockOwners[ic].owner = parent;
2594  ResourceOwnerRememberLock(parent, locallock);
2595  }
2596  else
2597  {
2598  /* Merge child's count with parent's */
2599  lockOwners[ip].nLocks += lockOwners[ic].nLocks;
2600  /* compact out unused slot */
2601  locallock->numLockOwners--;
2602  if (ic < locallock->numLockOwners)
2603  lockOwners[ic] = lockOwners[locallock->numLockOwners];
2604  }
2606 }
2607 
2608 /*
2609  * FastPathGrantRelationLock
2610  * Grant lock using per-backend fast-path array, if there is space.
2611  */
2612 static bool
2614 {
2615  uint32 f;
2616  uint32 unused_slot = FP_LOCK_SLOTS_PER_BACKEND;
2617 
2618  /* Scan for existing entry for this relid, remembering empty slot. */
2619  for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
2620  {
2621  if (FAST_PATH_GET_BITS(MyProc, f) == 0)
2622  unused_slot = f;
2623  else if (MyProc->fpRelId[f] == relid)
2624  {
2625  Assert(!FAST_PATH_CHECK_LOCKMODE(MyProc, f, lockmode));
2626  FAST_PATH_SET_LOCKMODE(MyProc, f, lockmode);
2627  return true;
2628  }
2629  }
2630 
2631  /* If no existing entry, use any empty slot. */
2632  if (unused_slot < FP_LOCK_SLOTS_PER_BACKEND)
2633  {
2634  MyProc->fpRelId[unused_slot] = relid;
2635  FAST_PATH_SET_LOCKMODE(MyProc, unused_slot, lockmode);
2637  return true;
2638  }
2639 
2640  /* No existing entry, and no empty slot. */
2641  return false;
2642 }
2643 
2644 /*
2645  * FastPathUnGrantRelationLock
2646  * Release fast-path lock, if present. Update backend-private local
2647  * use count, while we're at it.
2648  */
2649 static bool
2651 {
2652  uint32 f;
2653  bool result = false;
2654 
2656  for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
2657  {
2658  if (MyProc->fpRelId[f] == relid
2659  && FAST_PATH_CHECK_LOCKMODE(MyProc, f, lockmode))
2660  {
2661  Assert(!result);
2662  FAST_PATH_CLEAR_LOCKMODE(MyProc, f, lockmode);
2663  result = true;
2664  /* we continue iterating so as to update FastPathLocalUseCount */
2665  }
2666  if (FAST_PATH_GET_BITS(MyProc, f) != 0)
2668  }
2669  return result;
2670 }
2671 
2672 /*
2673  * FastPathTransferRelationLocks
2674  * Transfer locks matching the given lock tag from per-backend fast-path
2675  * arrays to the shared hash table.
2676  *
2677  * Returns true if successful, false if ran out of shared memory.
2678  */
2679 static bool
2680 FastPathTransferRelationLocks(LockMethod lockMethodTable, const LOCKTAG *locktag,
2681  uint32 hashcode)
2682 {
2683  LWLock *partitionLock = LockHashPartitionLock(hashcode);
2684  Oid relid = locktag->locktag_field2;
2685  uint32 i;
2686 
2687  /*
2688  * Every PGPROC that can potentially hold a fast-path lock is present in
2689  * ProcGlobal->allProcs. Prepared transactions are not, but any
2690  * outstanding fast-path locks held by prepared transactions are
2691  * transferred to the main lock table.
2692  */
2693  for (i = 0; i < ProcGlobal->allProcCount; i++)
2694  {
2695  PGPROC *proc = &ProcGlobal->allProcs[i];
2696  uint32 f;
2697 
2699 
2700  /*
2701  * If the target backend isn't referencing the same database as the
2702  * lock, then we needn't examine the individual relation IDs at all;
2703  * none of them can be relevant.
2704  *
2705  * proc->databaseId is set at backend startup time and never changes
2706  * thereafter, so it might be safe to perform this test before
2707  * acquiring &proc->fpInfoLock. In particular, it's certainly safe to
2708  * assume that if the target backend holds any fast-path locks, it
2709  * must have performed a memory-fencing operation (in particular, an
2710  * LWLock acquisition) since setting proc->databaseId. However, it's
2711  * less clear that our backend is certain to have performed a memory
2712  * fencing operation since the other backend set proc->databaseId. So
2713  * for now, we test it after acquiring the LWLock just to be safe.
2714  */
2715  if (proc->databaseId != locktag->locktag_field1)
2716  {
2717  LWLockRelease(&proc->fpInfoLock);
2718  continue;
2719  }
2720 
2721  for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
2722  {
2723  uint32 lockmode;
2724 
2725  /* Look for an allocated slot matching the given relid. */
2726  if (relid != proc->fpRelId[f] || FAST_PATH_GET_BITS(proc, f) == 0)
2727  continue;
2728 
2729  /* Find or create lock object. */
2730  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
2731  for (lockmode = FAST_PATH_LOCKNUMBER_OFFSET;
2733  ++lockmode)
2734  {
2735  PROCLOCK *proclock;
2736 
2737  if (!FAST_PATH_CHECK_LOCKMODE(proc, f, lockmode))
2738  continue;
2739  proclock = SetupLockInTable(lockMethodTable, proc, locktag,
2740  hashcode, lockmode);
2741  if (!proclock)
2742  {
2743  LWLockRelease(partitionLock);
2744  LWLockRelease(&proc->fpInfoLock);
2745  return false;
2746  }
2747  GrantLock(proclock->tag.myLock, proclock, lockmode);
2748  FAST_PATH_CLEAR_LOCKMODE(proc, f, lockmode);
2749  }
2750  LWLockRelease(partitionLock);
2751 
2752  /* No need to examine remaining slots. */
2753  break;
2754  }
2755  LWLockRelease(&proc->fpInfoLock);
2756  }
2757  return true;
2758 }
2759 
2760 /*
2761  * FastPathGetRelationLockEntry
2762  * Return the PROCLOCK for a lock originally taken via the fast-path,
2763  * transferring it to the primary lock table if necessary.
2764  *
2765  * Note: caller takes care of updating the locallock object.
2766  */
2767 static PROCLOCK *
2769 {
2770  LockMethod lockMethodTable = LockMethods[DEFAULT_LOCKMETHOD];
2771  LOCKTAG *locktag = &locallock->tag.lock;
2772  PROCLOCK *proclock = NULL;
2773  LWLock *partitionLock = LockHashPartitionLock(locallock->hashcode);
2774  Oid relid = locktag->locktag_field2;
2775  uint32 f;
2776 
2778 
2779  for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
2780  {
2781  uint32 lockmode;
2782 
2783  /* Look for an allocated slot matching the given relid. */
2784  if (relid != MyProc->fpRelId[f] || FAST_PATH_GET_BITS(MyProc, f) == 0)
2785  continue;
2786 
2787  /* If we don't have a lock of the given mode, forget it! */
2788  lockmode = locallock->tag.mode;
2789  if (!FAST_PATH_CHECK_LOCKMODE(MyProc, f, lockmode))
2790  break;
2791 
2792  /* Find or create lock object. */
2793  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
2794 
2795  proclock = SetupLockInTable(lockMethodTable, MyProc, locktag,
2796  locallock->hashcode, lockmode);
2797  if (!proclock)
2798  {
2799  LWLockRelease(partitionLock);
2801  ereport(ERROR,
2802  (errcode(ERRCODE_OUT_OF_MEMORY),
2803  errmsg("out of shared memory"),
2804  errhint("You might need to increase %s.", "max_locks_per_transaction")));
2805  }
2806  GrantLock(proclock->tag.myLock, proclock, lockmode);
2807  FAST_PATH_CLEAR_LOCKMODE(MyProc, f, lockmode);
2808 
2809  LWLockRelease(partitionLock);
2810 
2811  /* No need to examine remaining slots. */
2812  break;
2813  }
2814 
2816 
2817  /* Lock may have already been transferred by some other backend. */
2818  if (proclock == NULL)
2819  {
2820  LOCK *lock;
2821  PROCLOCKTAG proclocktag;
2822  uint32 proclock_hashcode;
2823 
2824  LWLockAcquire(partitionLock, LW_SHARED);
2825 
2827  locktag,
2828  locallock->hashcode,
2829  HASH_FIND,
2830  NULL);
2831  if (!lock)
2832  elog(ERROR, "failed to re-find shared lock object");
2833 
2834  proclocktag.myLock = lock;
2835  proclocktag.myProc = MyProc;
2836 
2837  proclock_hashcode = ProcLockHashCode(&proclocktag, locallock->hashcode);
2838  proclock = (PROCLOCK *)
2840  &proclocktag,
2841  proclock_hashcode,
2842  HASH_FIND,
2843  NULL);
2844  if (!proclock)
2845  elog(ERROR, "failed to re-find shared proclock object");
2846  LWLockRelease(partitionLock);
2847  }
2848 
2849  return proclock;
2850 }
2851 
2852 /*
2853  * GetLockConflicts
2854  * Get an array of VirtualTransactionIds of xacts currently holding locks
2855  * that would conflict with the specified lock/lockmode.
2856  * xacts merely awaiting such a lock are NOT reported.
2857  *
2858  * The result array is palloc'd and is terminated with an invalid VXID.
2859  * *countp, if not null, is updated to the number of items set.
2860  *
2861  * Of course, the result could be out of date by the time it's returned, so
2862  * use of this function has to be thought about carefully. Similarly, a
2863  * PGPROC with no "lxid" will be considered non-conflicting regardless of any
2864  * lock it holds. Existing callers don't care about a locker after that
2865  * locker's pg_xact updates complete. CommitTransaction() clears "lxid" after
2866  * pg_xact updates and before releasing locks.
2867  *
2868  * Note we never include the current xact's vxid in the result array,
2869  * since an xact never blocks itself.
2870  */
2872 GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode, int *countp)
2873 {
2874  static VirtualTransactionId *vxids;
2875  LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
2876  LockMethod lockMethodTable;
2877  LOCK *lock;
2878  LOCKMASK conflictMask;
2879  dlist_iter proclock_iter;
2880  PROCLOCK *proclock;
2881  uint32 hashcode;
2882  LWLock *partitionLock;
2883  int count = 0;
2884  int fast_count = 0;
2885 
2886  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
2887  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
2888  lockMethodTable = LockMethods[lockmethodid];
2889  if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
2890  elog(ERROR, "unrecognized lock mode: %d", lockmode);
2891 
2892  /*
2893  * Allocate memory to store results, and fill with InvalidVXID. We only
2894  * need enough space for MaxBackends + max_prepared_xacts + a terminator.
2895  * InHotStandby allocate once in TopMemoryContext.
2896  */
2897  if (InHotStandby)
2898  {
2899  if (vxids == NULL)
2900  vxids = (VirtualTransactionId *)
2902  sizeof(VirtualTransactionId) *
2904  }
2905  else
2906  vxids = (VirtualTransactionId *)
2907  palloc0(sizeof(VirtualTransactionId) *
2909 
2910  /* Compute hash code and partition lock, and look up conflicting modes. */
2911  hashcode = LockTagHashCode(locktag);
2912  partitionLock = LockHashPartitionLock(hashcode);
2913  conflictMask = lockMethodTable->conflictTab[lockmode];
2914 
2915  /*
2916  * Fast path locks might not have been entered in the primary lock table.
2917  * If the lock we're dealing with could conflict with such a lock, we must
2918  * examine each backend's fast-path array for conflicts.
2919  */
2920  if (ConflictsWithRelationFastPath(locktag, lockmode))
2921  {
2922  int i;
2923  Oid relid = locktag->locktag_field2;
2924  VirtualTransactionId vxid;
2925 
2926  /*
2927  * Iterate over relevant PGPROCs. Anything held by a prepared
2928  * transaction will have been transferred to the primary lock table,
2929  * so we need not worry about those. This is all a bit fuzzy, because
2930  * new locks could be taken after we've visited a particular
2931  * partition, but the callers had better be prepared to deal with that
2932  * anyway, since the locks could equally well be taken between the
2933  * time we return the value and the time the caller does something
2934  * with it.
2935  */
2936  for (i = 0; i < ProcGlobal->allProcCount; i++)
2937  {
2938  PGPROC *proc = &ProcGlobal->allProcs[i];
2939  uint32 f;
2940 
2941  /* A backend never blocks itself */
2942  if (proc == MyProc)
2943  continue;
2944 
2946 
2947  /*
2948  * If the target backend isn't referencing the same database as
2949  * the lock, then we needn't examine the individual relation IDs
2950  * at all; none of them can be relevant.
2951  *
2952  * See FastPathTransferRelationLocks() for discussion of why we do
2953  * this test after acquiring the lock.
2954  */
2955  if (proc->databaseId != locktag->locktag_field1)
2956  {
2957  LWLockRelease(&proc->fpInfoLock);
2958  continue;
2959  }
2960 
2961  for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
2962  {
2963  uint32 lockmask;
2964 
2965  /* Look for an allocated slot matching the given relid. */
2966  if (relid != proc->fpRelId[f])
2967  continue;
2968  lockmask = FAST_PATH_GET_BITS(proc, f);
2969  if (!lockmask)
2970  continue;
2971  lockmask <<= FAST_PATH_LOCKNUMBER_OFFSET;
2972 
2973  /*
2974  * There can only be one entry per relation, so if we found it
2975  * and it doesn't conflict, we can skip the rest of the slots.
2976  */
2977  if ((lockmask & conflictMask) == 0)
2978  break;
2979 
2980  /* Conflict! */
2981  GET_VXID_FROM_PGPROC(vxid, *proc);
2982 
2983  if (VirtualTransactionIdIsValid(vxid))
2984  vxids[count++] = vxid;
2985  /* else, xact already committed or aborted */
2986 
2987  /* No need to examine remaining slots. */
2988  break;
2989  }
2990 
2991  LWLockRelease(&proc->fpInfoLock);
2992  }
2993  }
2994 
2995  /* Remember how many fast-path conflicts we found. */
2996  fast_count = count;
2997 
2998  /*
2999  * Look up the lock object matching the tag.
3000  */
3001  LWLockAcquire(partitionLock, LW_SHARED);
3002 
3004  locktag,
3005  hashcode,
3006  HASH_FIND,
3007  NULL);
3008  if (!lock)
3009  {
3010  /*
3011  * If the lock object doesn't exist, there is nothing holding a lock
3012  * on this lockable object.
3013  */
3014  LWLockRelease(partitionLock);
3015  vxids[count].procNumber = INVALID_PROC_NUMBER;
3017  if (countp)
3018  *countp = count;
3019  return vxids;
3020  }
3021 
3022  /*
3023  * Examine each existing holder (or awaiter) of the lock.
3024  */
3025  dlist_foreach(proclock_iter, &lock->procLocks)
3026  {
3027  proclock = dlist_container(PROCLOCK, lockLink, proclock_iter.cur);
3028 
3029  if (conflictMask & proclock->holdMask)
3030  {
3031  PGPROC *proc = proclock->tag.myProc;
3032 
3033  /* A backend never blocks itself */
3034  if (proc != MyProc)
3035  {
3036  VirtualTransactionId vxid;
3037 
3038  GET_VXID_FROM_PGPROC(vxid, *proc);
3039 
3040  if (VirtualTransactionIdIsValid(vxid))
3041  {
3042  int i;
3043 
3044  /* Avoid duplicate entries. */
3045  for (i = 0; i < fast_count; ++i)
3046  if (VirtualTransactionIdEquals(vxids[i], vxid))
3047  break;
3048  if (i >= fast_count)
3049  vxids[count++] = vxid;
3050  }
3051  /* else, xact already committed or aborted */
3052  }
3053  }
3054  }
3055 
3056  LWLockRelease(partitionLock);
3057 
3058  if (count > MaxBackends + max_prepared_xacts) /* should never happen */
3059  elog(PANIC, "too many conflicting locks found");
3060 
3061  vxids[count].procNumber = INVALID_PROC_NUMBER;
3063  if (countp)
3064  *countp = count;
3065  return vxids;
3066 }
3067 
3068 /*
3069  * Find a lock in the shared lock table and release it. It is the caller's
3070  * responsibility to verify that this is a sane thing to do. (For example, it
3071  * would be bad to release a lock here if there might still be a LOCALLOCK
3072  * object with pointers to it.)
3073  *
3074  * We currently use this in two situations: first, to release locks held by
3075  * prepared transactions on commit (see lock_twophase_postcommit); and second,
3076  * to release locks taken via the fast-path, transferred to the main hash
3077  * table, and then released (see LockReleaseAll).
3078  */
3079 static void
3080 LockRefindAndRelease(LockMethod lockMethodTable, PGPROC *proc,
3081  LOCKTAG *locktag, LOCKMODE lockmode,
3082  bool decrement_strong_lock_count)
3083 {
3084  LOCK *lock;
3085  PROCLOCK *proclock;
3086  PROCLOCKTAG proclocktag;
3087  uint32 hashcode;
3088  uint32 proclock_hashcode;
3089  LWLock *partitionLock;
3090  bool wakeupNeeded;
3091 
3092  hashcode = LockTagHashCode(locktag);
3093  partitionLock = LockHashPartitionLock(hashcode);
3094 
3095  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
3096 
3097  /*
3098  * Re-find the lock object (it had better be there).
3099  */
3101  locktag,
3102  hashcode,
3103  HASH_FIND,
3104  NULL);
3105  if (!lock)
3106  elog(PANIC, "failed to re-find shared lock object");
3107 
3108  /*
3109  * Re-find the proclock object (ditto).
3110  */
3111  proclocktag.myLock = lock;
3112  proclocktag.myProc = proc;
3113 
3114  proclock_hashcode = ProcLockHashCode(&proclocktag, hashcode);
3115 
3117  &proclocktag,
3118  proclock_hashcode,
3119  HASH_FIND,
3120  NULL);
3121  if (!proclock)
3122  elog(PANIC, "failed to re-find shared proclock object");
3123 
3124  /*
3125  * Double-check that we are actually holding a lock of the type we want to
3126  * release.
3127  */
3128  if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
3129  {
3130  PROCLOCK_PRINT("lock_twophase_postcommit: WRONGTYPE", proclock);
3131  LWLockRelease(partitionLock);
3132  elog(WARNING, "you don't own a lock of type %s",
3133  lockMethodTable->lockModeNames[lockmode]);
3134  return;
3135  }
3136 
3137  /*
3138  * Do the releasing. CleanUpLock will waken any now-wakable waiters.
3139  */
3140  wakeupNeeded = UnGrantLock(lock, lockmode, proclock, lockMethodTable);
3141 
3142  CleanUpLock(lock, proclock,
3143  lockMethodTable, hashcode,
3144  wakeupNeeded);
3145 
3146  LWLockRelease(partitionLock);
3147 
3148  /*
3149  * Decrement strong lock count. This logic is needed only for 2PC.
3150  */
3151  if (decrement_strong_lock_count
3152  && ConflictsWithRelationFastPath(locktag, lockmode))
3153  {
3154  uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
3155 
3157  Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
3158  FastPathStrongRelationLocks->count[fasthashcode]--;
3160  }
3161 }
3162 
3163 /*
3164  * CheckForSessionAndXactLocks
3165  * Check to see if transaction holds both session-level and xact-level
3166  * locks on the same object; if so, throw an error.
3167  *
3168  * If we have both session- and transaction-level locks on the same object,
3169  * PREPARE TRANSACTION must fail. This should never happen with regular
3170  * locks, since we only take those at session level in some special operations
3171  * like VACUUM. It's possible to hit this with advisory locks, though.
3172  *
3173  * It would be nice if we could keep the session hold and give away the
3174  * transactional hold to the prepared xact. However, that would require two
3175  * PROCLOCK objects, and we cannot be sure that another PROCLOCK will be
3176  * available when it comes time for PostPrepare_Locks to do the deed.
3177  * So for now, we error out while we can still do so safely.
3178  *
3179  * Since the LOCALLOCK table stores a separate entry for each lockmode,
3180  * we can't implement this check by examining LOCALLOCK entries in isolation.
3181  * We must build a transient hashtable that is indexed by locktag only.
3182  */
3183 static void
3185 {
3186  typedef struct
3187  {
3188  LOCKTAG lock; /* identifies the lockable object */
3189  bool sessLock; /* is any lockmode held at session level? */
3190  bool xactLock; /* is any lockmode held at xact level? */
3191  } PerLockTagEntry;
3192 
3193  HASHCTL hash_ctl;
3194  HTAB *lockhtab;
3195  HASH_SEQ_STATUS status;
3196  LOCALLOCK *locallock;
3197 
3198  /* Create a local hash table keyed by LOCKTAG only */
3199  hash_ctl.keysize = sizeof(LOCKTAG);
3200  hash_ctl.entrysize = sizeof(PerLockTagEntry);
3201  hash_ctl.hcxt = CurrentMemoryContext;
3202 
3203  lockhtab = hash_create("CheckForSessionAndXactLocks table",
3204  256, /* arbitrary initial size */
3205  &hash_ctl,
3207 
3208  /* Scan local lock table to find entries for each LOCKTAG */
3210 
3211  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
3212  {
3213  LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
3214  PerLockTagEntry *hentry;
3215  bool found;
3216  int i;
3217 
3218  /*
3219  * Ignore VXID locks. We don't want those to be held by prepared
3220  * transactions, since they aren't meaningful after a restart.
3221  */
3222  if (locallock->tag.lock.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
3223  continue;
3224 
3225  /* Ignore it if we don't actually hold the lock */
3226  if (locallock->nLocks <= 0)
3227  continue;
3228 
3229  /* Otherwise, find or make an entry in lockhtab */
3230  hentry = (PerLockTagEntry *) hash_search(lockhtab,
3231  &locallock->tag.lock,
3232  HASH_ENTER, &found);
3233  if (!found) /* initialize, if newly created */
3234  hentry->sessLock = hentry->xactLock = false;
3235 
3236  /* Scan to see if we hold lock at session or xact level or both */
3237  for (i = locallock->numLockOwners - 1; i >= 0; i--)
3238  {
3239  if (lockOwners[i].owner == NULL)
3240  hentry->sessLock = true;
3241  else
3242  hentry->xactLock = true;
3243  }
3244 
3245  /*
3246  * We can throw error immediately when we see both types of locks; no
3247  * need to wait around to see if there are more violations.
3248  */
3249  if (hentry->sessLock && hentry->xactLock)
3250  ereport(ERROR,
3251  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
3252  errmsg("cannot PREPARE while holding both session-level and transaction-level locks on the same object")));
3253  }
3254 
3255  /* Success, so clean up */
3256  hash_destroy(lockhtab);
3257 }
3258 
3259 /*
3260  * AtPrepare_Locks
3261  * Do the preparatory work for a PREPARE: make 2PC state file records
3262  * for all locks currently held.
3263  *
3264  * Session-level locks are ignored, as are VXID locks.
3265  *
3266  * For the most part, we don't need to touch shared memory for this ---
3267  * all the necessary state information is in the locallock table.
3268  * Fast-path locks are an exception, however: we move any such locks to
3269  * the main table before allowing PREPARE TRANSACTION to succeed.
3270  */
3271 void
3273 {
3274  HASH_SEQ_STATUS status;
3275  LOCALLOCK *locallock;
3276 
3277  /* First, verify there aren't locks of both xact and session level */
3279 
3280  /* Now do the per-locallock cleanup work */
3282 
3283  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
3284  {
3285  TwoPhaseLockRecord record;
3286  LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
3287  bool haveSessionLock;
3288  bool haveXactLock;
3289  int i;
3290 
3291  /*
3292  * Ignore VXID locks. We don't want those to be held by prepared
3293  * transactions, since they aren't meaningful after a restart.
3294  */
3295  if (locallock->tag.lock.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
3296  continue;
3297 
3298  /* Ignore it if we don't actually hold the lock */
3299  if (locallock->nLocks <= 0)
3300  continue;
3301 
3302  /* Scan to see whether we hold it at session or transaction level */
3303  haveSessionLock = haveXactLock = false;
3304  for (i = locallock->numLockOwners - 1; i >= 0; i--)
3305  {
3306  if (lockOwners[i].owner == NULL)
3307  haveSessionLock = true;
3308  else
3309  haveXactLock = true;
3310  }
3311 
3312  /* Ignore it if we have only session lock */
3313  if (!haveXactLock)
3314  continue;
3315 
3316  /* This can't happen, because we already checked it */
3317  if (haveSessionLock)
3318  ereport(ERROR,
3319  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
3320  errmsg("cannot PREPARE while holding both session-level and transaction-level locks on the same object")));
3321 
3322  /*
3323  * If the local lock was taken via the fast-path, we need to move it
3324  * to the primary lock table, or just get a pointer to the existing
3325  * primary lock table entry if by chance it's already been
3326  * transferred.
3327  */
3328  if (locallock->proclock == NULL)
3329  {
3330  locallock->proclock = FastPathGetRelationLockEntry(locallock);
3331  locallock->lock = locallock->proclock->tag.myLock;
3332  }
3333 
3334  /*
3335  * Arrange to not release any strong lock count held by this lock
3336  * entry. We must retain the count until the prepared transaction is
3337  * committed or rolled back.
3338  */
3339  locallock->holdsStrongLockCount = false;
3340 
3341  /*
3342  * Create a 2PC record.
3343  */
3344  memcpy(&(record.locktag), &(locallock->tag.lock), sizeof(LOCKTAG));
3345  record.lockmode = locallock->tag.mode;
3346 
3348  &record, sizeof(TwoPhaseLockRecord));
3349  }
3350 }
3351 
3352 /*
3353  * PostPrepare_Locks
3354  * Clean up after successful PREPARE
3355  *
3356  * Here, we want to transfer ownership of our locks to a dummy PGPROC
3357  * that's now associated with the prepared transaction, and we want to
3358  * clean out the corresponding entries in the LOCALLOCK table.
3359  *
3360  * Note: by removing the LOCALLOCK entries, we are leaving dangling
3361  * pointers in the transaction's resource owner. This is OK at the
3362  * moment since resowner.c doesn't try to free locks retail at a toplevel
3363  * transaction commit or abort. We could alternatively zero out nLocks
3364  * and leave the LOCALLOCK entries to be garbage-collected by LockReleaseAll,
3365  * but that probably costs more cycles.
3366  */
3367 void
3369 {
3370  PGPROC *newproc = TwoPhaseGetDummyProc(xid, false);
3371  HASH_SEQ_STATUS status;
3372  LOCALLOCK *locallock;
3373  LOCK *lock;
3374  PROCLOCK *proclock;
3375  PROCLOCKTAG proclocktag;
3376  int partition;
3377 
3378  /* Can't prepare a lock group follower. */
3379  Assert(MyProc->lockGroupLeader == NULL ||
3381 
3382  /* This is a critical section: any error means big trouble */
3384 
3385  /*
3386  * First we run through the locallock table and get rid of unwanted
3387  * entries, then we scan the process's proclocks and transfer them to the
3388  * target proc.
3389  *
3390  * We do this separately because we may have multiple locallock entries
3391  * pointing to the same proclock, and we daren't end up with any dangling
3392  * pointers.
3393  */
3395 
3396  while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
3397  {
3398  LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
3399  bool haveSessionLock;
3400  bool haveXactLock;
3401  int i;
3402 
3403  if (locallock->proclock == NULL || locallock->lock == NULL)
3404  {
3405  /*
3406  * We must've run out of shared memory while trying to set up this
3407  * lock. Just forget the local entry.
3408  */
3409  Assert(locallock->nLocks == 0);
3410  RemoveLocalLock(locallock);
3411  continue;
3412  }
3413 
3414  /* Ignore VXID locks */
3415  if (locallock->tag.lock.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
3416  continue;
3417 
3418  /* Scan to see whether we hold it at session or transaction level */
3419  haveSessionLock = haveXactLock = false;
3420  for (i = locallock->numLockOwners - 1; i >= 0; i--)
3421  {
3422  if (lockOwners[i].owner == NULL)
3423  haveSessionLock = true;
3424  else
3425  haveXactLock = true;
3426  }
3427 
3428  /* Ignore it if we have only session lock */
3429  if (!haveXactLock)
3430  continue;
3431 
3432  /* This can't happen, because we already checked it */
3433  if (haveSessionLock)
3434  ereport(PANIC,
3435  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
3436  errmsg("cannot PREPARE while holding both session-level and transaction-level locks on the same object")));
3437 
3438  /* Mark the proclock to show we need to release this lockmode */
3439  if (locallock->nLocks > 0)
3440  locallock->proclock->releaseMask |= LOCKBIT_ON(locallock->tag.mode);
3441 
3442  /* And remove the locallock hashtable entry */
3443  RemoveLocalLock(locallock);
3444  }
3445 
3446  /*
3447  * Now, scan each lock partition separately.
3448  */
3449  for (partition = 0; partition < NUM_LOCK_PARTITIONS; partition++)
3450  {
3451  LWLock *partitionLock;
3452  dlist_head *procLocks = &(MyProc->myProcLocks[partition]);
3453  dlist_mutable_iter proclock_iter;
3454 
3455  partitionLock = LockHashPartitionLockByIndex(partition);
3456 
3457  /*
3458  * If the proclock list for this partition is empty, we can skip
3459  * acquiring the partition lock. This optimization is safer than the
3460  * situation in LockReleaseAll, because we got rid of any fast-path
3461  * locks during AtPrepare_Locks, so there cannot be any case where
3462  * another backend is adding something to our lists now. For safety,
3463  * though, we code this the same way as in LockReleaseAll.
3464  */
3465  if (dlist_is_empty(procLocks))
3466  continue; /* needn't examine this partition */
3467 
3468  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
3469 
3470  dlist_foreach_modify(proclock_iter, procLocks)
3471  {
3472  proclock = dlist_container(PROCLOCK, procLink, proclock_iter.cur);
3473 
3474  Assert(proclock->tag.myProc == MyProc);
3475 
3476  lock = proclock->tag.myLock;
3477 
3478  /* Ignore VXID locks */
3480  continue;
3481 
3482  PROCLOCK_PRINT("PostPrepare_Locks", proclock);
3483  LOCK_PRINT("PostPrepare_Locks", lock, 0);
3484  Assert(lock->nRequested >= 0);
3485  Assert(lock->nGranted >= 0);
3486  Assert(lock->nGranted <= lock->nRequested);
3487  Assert((proclock->holdMask & ~lock->grantMask) == 0);
3488 
3489  /* Ignore it if nothing to release (must be a session lock) */
3490  if (proclock->releaseMask == 0)
3491  continue;
3492 
3493  /* Else we should be releasing all locks */
3494  if (proclock->releaseMask != proclock->holdMask)
3495  elog(PANIC, "we seem to have dropped a bit somewhere");
3496 
3497  /*
3498  * We cannot simply modify proclock->tag.myProc to reassign
3499  * ownership of the lock, because that's part of the hash key and
3500  * the proclock would then be in the wrong hash chain. Instead
3501  * use hash_update_hash_key. (We used to create a new hash entry,
3502  * but that risks out-of-memory failure if other processes are
3503  * busy making proclocks too.) We must unlink the proclock from
3504  * our procLink chain and put it into the new proc's chain, too.
3505  *
3506  * Note: the updated proclock hash key will still belong to the
3507  * same hash partition, cf proclock_hash(). So the partition lock
3508  * we already hold is sufficient for this.
3509  */
3510  dlist_delete(&proclock->procLink);
3511 
3512  /*
3513  * Create the new hash key for the proclock.
3514  */
3515  proclocktag.myLock = lock;
3516  proclocktag.myProc = newproc;
3517 
3518  /*
3519  * Update groupLeader pointer to point to the new proc. (We'd
3520  * better not be a member of somebody else's lock group!)
3521  */
3522  Assert(proclock->groupLeader == proclock->tag.myProc);
3523  proclock->groupLeader = newproc;
3524 
3525  /*
3526  * Update the proclock. We should not find any existing entry for
3527  * the same hash key, since there can be only one entry for any
3528  * given lock with my own proc.
3529  */
3531  proclock,
3532  &proclocktag))
3533  elog(PANIC, "duplicate entry found while reassigning a prepared transaction's locks");
3534 
3535  /* Re-link into the new proc's proclock list */
3536  dlist_push_tail(&newproc->myProcLocks[partition], &proclock->procLink);
3537 
3538  PROCLOCK_PRINT("PostPrepare_Locks: updated", proclock);
3539  } /* loop over PROCLOCKs within this partition */
3540 
3541  LWLockRelease(partitionLock);
3542  } /* loop over partitions */
3543 
3544  END_CRIT_SECTION();
3545 }
3546 
3547 
3548 /*
3549  * Estimate shared-memory space used for lock tables
3550  */
3551 Size
3553 {
3554  Size size = 0;
3555  long max_table_size;
3556 
3557  /* lock hash table */
3558  max_table_size = NLOCKENTS();
3559  size = add_size(size, hash_estimate_size(max_table_size, sizeof(LOCK)));
3560 
3561  /* proclock hash table */
3562  max_table_size *= 2;
3563  size = add_size(size, hash_estimate_size(max_table_size, sizeof(PROCLOCK)));
3564 
3565  /*
3566  * Since NLOCKENTS is only an estimate, add 10% safety margin.
3567  */
3568  size = add_size(size, size / 10);
3569 
3570  return size;
3571 }
3572 
3573 /*
3574  * GetLockStatusData - Return a summary of the lock manager's internal
3575  * status, for use in a user-level reporting function.
3576  *
3577  * The return data consists of an array of LockInstanceData objects,
3578  * which are a lightly abstracted version of the PROCLOCK data structures,
3579  * i.e. there is one entry for each unique lock and interested PGPROC.
3580  * It is the caller's responsibility to match up related items (such as
3581  * references to the same lockable object or PGPROC) if wanted.
3582  *
3583  * The design goal is to hold the LWLocks for as short a time as possible;
3584  * thus, this function simply makes a copy of the necessary data and releases
3585  * the locks, allowing the caller to contemplate and format the data for as
3586  * long as it pleases.
3587  */
3588 LockData *
3590 {
3591  LockData *data;
3592  PROCLOCK *proclock;
3593  HASH_SEQ_STATUS seqstat;
3594  int els;
3595  int el;
3596  int i;
3597 
3598  data = (LockData *) palloc(sizeof(LockData));
3599 
3600  /* Guess how much space we'll need. */
3601  els = MaxBackends;
3602  el = 0;
3603  data->locks = (LockInstanceData *) palloc(sizeof(LockInstanceData) * els);
3604 
3605  /*
3606  * First, we iterate through the per-backend fast-path arrays, locking
3607  * them one at a time. This might produce an inconsistent picture of the
3608  * system state, but taking all of those LWLocks at the same time seems
3609  * impractical (in particular, note MAX_SIMUL_LWLOCKS). It shouldn't
3610  * matter too much, because none of these locks can be involved in lock
3611  * conflicts anyway - anything that might must be present in the main lock
3612  * table. (For the same reason, we don't sweat about making leaderPid
3613  * completely valid. We cannot safely dereference another backend's
3614  * lockGroupLeader field without holding all lock partition locks, and
3615  * it's not worth that.)
3616  */
3617  for (i = 0; i < ProcGlobal->allProcCount; ++i)
3618  {
3619  PGPROC *proc = &ProcGlobal->allProcs[i];
3620  uint32 f;
3621 
3623 
3624  for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; ++f)
3625  {
3626  LockInstanceData *instance;
3627  uint32 lockbits = FAST_PATH_GET_BITS(proc, f);
3628 
3629  /* Skip unallocated slots. */
3630  if (!lockbits)
3631  continue;
3632 
3633  if (el >= els)
3634  {
3635  els += MaxBackends;
3636  data->locks = (LockInstanceData *)
3637  repalloc(data->locks, sizeof(LockInstanceData) * els);
3638  }
3639 
3640  instance = &data->locks[el];
3641  SET_LOCKTAG_RELATION(instance->locktag, proc->databaseId,
3642  proc->fpRelId[f]);
3643  instance->holdMask = lockbits << FAST_PATH_LOCKNUMBER_OFFSET;
3644  instance->waitLockMode = NoLock;
3645  instance->vxid.procNumber = proc->vxid.procNumber;
3646  instance->vxid.localTransactionId = proc->vxid.lxid;
3647  instance->pid = proc->pid;
3648  instance->leaderPid = proc->pid;
3649  instance->fastpath = true;
3650 
3651  /*
3652  * Successfully taking fast path lock means there were no
3653  * conflicting locks.
3654  */
3655  instance->waitStart = 0;
3656 
3657  el++;
3658  }
3659 
3660  if (proc->fpVXIDLock)
3661  {
3662  VirtualTransactionId vxid;
3663  LockInstanceData *instance;
3664 
3665  if (el >= els)
3666  {
3667  els += MaxBackends;
3668  data->locks = (LockInstanceData *)
3669  repalloc(data->locks, sizeof(LockInstanceData) * els);
3670  }
3671 
3672  vxid.procNumber = proc->vxid.procNumber;
3674 
3675  instance = &data->locks[el];
3676  SET_LOCKTAG_VIRTUALTRANSACTION(instance->locktag, vxid);
3677  instance->holdMask = LOCKBIT_ON(ExclusiveLock);
3678  instance->waitLockMode = NoLock;
3679  instance->vxid.procNumber = proc->vxid.procNumber;
3680  instance->vxid.localTransactionId = proc->vxid.lxid;
3681  instance->pid = proc->pid;
3682  instance->leaderPid = proc->pid;
3683  instance->fastpath = true;
3684  instance->waitStart = 0;
3685 
3686  el++;
3687  }
3688 
3689  LWLockRelease(&proc->fpInfoLock);
3690  }
3691 
3692  /*
3693  * Next, acquire lock on the entire shared lock data structure. We do
3694  * this so that, at least for locks in the primary lock table, the state
3695  * will be self-consistent.
3696  *
3697  * Since this is a read-only operation, we take shared instead of
3698  * exclusive lock. There's not a whole lot of point to this, because all
3699  * the normal operations require exclusive lock, but it doesn't hurt
3700  * anything either. It will at least allow two backends to do
3701  * GetLockStatusData in parallel.
3702  *
3703  * Must grab LWLocks in partition-number order to avoid LWLock deadlock.
3704  */
3705  for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
3707 
3708  /* Now we can safely count the number of proclocks */
3710  if (data->nelements > els)
3711  {
3712  els = data->nelements;
3713  data->locks = (LockInstanceData *)
3714  repalloc(data->locks, sizeof(LockInstanceData) * els);
3715  }
3716 
3717  /* Now scan the tables to copy the data */
3719 
3720  while ((proclock = (PROCLOCK *) hash_seq_search(&seqstat)))
3721  {
3722  PGPROC *proc = proclock->tag.myProc;
3723  LOCK *lock = proclock->tag.myLock;
3724  LockInstanceData *instance = &data->locks[el];
3725 
3726  memcpy(&instance->locktag, &lock->tag, sizeof(LOCKTAG));
3727  instance->holdMask = proclock->holdMask;
3728  if (proc->waitLock == proclock->tag.myLock)
3729  instance->waitLockMode = proc->waitLockMode;
3730  else
3731  instance->waitLockMode = NoLock;
3732  instance->vxid.procNumber = proc->vxid.procNumber;
3733  instance->vxid.localTransactionId = proc->vxid.lxid;
3734  instance->pid = proc->pid;
3735  instance->leaderPid = proclock->groupLeader->pid;
3736  instance->fastpath = false;
3737  instance->waitStart = (TimestampTz) pg_atomic_read_u64(&proc->waitStart);
3738 
3739  el++;
3740  }
3741 
3742  /*
3743  * And release locks. We do this in reverse order for two reasons: (1)
3744  * Anyone else who needs more than one of the locks will be trying to lock
3745  * them in increasing order; we don't want to release the other process
3746  * until it can get all the locks it needs. (2) This avoids O(N^2)
3747  * behavior inside LWLockRelease.
3748  */
3749  for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
3751 
3752  Assert(el == data->nelements);
3753 
3754  return data;
3755 }
3756 
3757 /*
3758  * GetBlockerStatusData - Return a summary of the lock manager's state
3759  * concerning locks that are blocking the specified PID or any member of
3760  * the PID's lock group, for use in a user-level reporting function.
3761  *
3762  * For each PID within the lock group that is awaiting some heavyweight lock,
3763  * the return data includes an array of LockInstanceData objects, which are
3764  * the same data structure used by GetLockStatusData; but unlike that function,
3765  * this one reports only the PROCLOCKs associated with the lock that that PID
3766  * is blocked on. (Hence, all the locktags should be the same for any one
3767  * blocked PID.) In addition, we return an array of the PIDs of those backends
3768  * that are ahead of the blocked PID in the lock's wait queue. These can be
3769  * compared with the PIDs in the LockInstanceData objects to determine which
3770  * waiters are ahead of or behind the blocked PID in the queue.
3771  *
3772  * If blocked_pid isn't a valid backend PID or nothing in its lock group is
3773  * waiting on any heavyweight lock, return empty arrays.
3774  *
3775  * The design goal is to hold the LWLocks for as short a time as possible;
3776  * thus, this function simply makes a copy of the necessary data and releases
3777  * the locks, allowing the caller to contemplate and format the data for as
3778  * long as it pleases.
3779  */
3781 GetBlockerStatusData(int blocked_pid)
3782 {
3784  PGPROC *proc;
3785  int i;
3786 
3788 
3789  /*
3790  * Guess how much space we'll need, and preallocate. Most of the time
3791  * this will avoid needing to do repalloc while holding the LWLocks. (We
3792  * assume, but check with an Assert, that MaxBackends is enough entries
3793  * for the procs[] array; the other two could need enlargement, though.)
3794  */
3795  data->nprocs = data->nlocks = data->npids = 0;
3796  data->maxprocs = data->maxlocks = data->maxpids = MaxBackends;
3797  data->procs = (BlockedProcData *) palloc(sizeof(BlockedProcData) * data->maxprocs);
3798  data->locks = (LockInstanceData *) palloc(sizeof(LockInstanceData) * data->maxlocks);
3799  data->waiter_pids = (int *) palloc(sizeof(int) * data->maxpids);
3800 
3801  /*
3802  * In order to search the ProcArray for blocked_pid and assume that that
3803  * entry won't immediately disappear under us, we must hold ProcArrayLock.
3804  * In addition, to examine the lock grouping fields of any other backend,
3805  * we must hold all the hash partition locks. (Only one of those locks is
3806  * actually relevant for any one lock group, but we can't know which one
3807  * ahead of time.) It's fairly annoying to hold all those locks
3808  * throughout this, but it's no worse than GetLockStatusData(), and it
3809  * does have the advantage that we're guaranteed to return a
3810  * self-consistent instantaneous state.
3811  */
3812  LWLockAcquire(ProcArrayLock, LW_SHARED);
3813 
3814  proc = BackendPidGetProcWithLock(blocked_pid);
3815 
3816  /* Nothing to do if it's gone */
3817  if (proc != NULL)
3818  {
3819  /*
3820  * Acquire lock on the entire shared lock data structure. See notes
3821  * in GetLockStatusData().
3822  */
3823  for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
3825 
3826  if (proc->lockGroupLeader == NULL)
3827  {
3828  /* Easy case, proc is not a lock group member */
3830  }
3831  else
3832  {
3833  /* Examine all procs in proc's lock group */
3834  dlist_iter iter;
3835 
3837  {
3838  PGPROC *memberProc;
3839 
3840  memberProc = dlist_container(PGPROC, lockGroupLink, iter.cur);
3841  GetSingleProcBlockerStatusData(memberProc, data);
3842  }
3843  }
3844 
3845  /*
3846  * And release locks. See notes in GetLockStatusData().
3847  */
3848  for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
3850 
3851  Assert(data->nprocs <= data->maxprocs);
3852  }
3853 
3854  LWLockRelease(ProcArrayLock);
3855 
3856  return data;
3857 }
3858 
3859 /* Accumulate data about one possibly-blocked proc for GetBlockerStatusData */
3860 static void
3862 {
3863  LOCK *theLock = blocked_proc->waitLock;
3864  BlockedProcData *bproc;
3865  dlist_iter proclock_iter;
3866  dlist_iter proc_iter;
3867  dclist_head *waitQueue;
3868  int queue_size;
3869 
3870  /* Nothing to do if this proc is not blocked */
3871  if (theLock == NULL)
3872  return;
3873 
3874  /* Set up a procs[] element */
3875  bproc = &data->procs[data->nprocs++];
3876  bproc->pid = blocked_proc->pid;
3877  bproc->first_lock = data->nlocks;
3878  bproc->first_waiter = data->npids;
3879 
3880  /*
3881  * We may ignore the proc's fast-path arrays, since nothing in those could
3882  * be related to a contended lock.
3883  */
3884 
3885  /* Collect all PROCLOCKs associated with theLock */
3886  dlist_foreach(proclock_iter, &theLock->procLocks)
3887  {
3888  PROCLOCK *proclock =
3889  dlist_container(PROCLOCK, lockLink, proclock_iter.cur);
3890  PGPROC *proc = proclock->tag.myProc;
3891  LOCK *lock = proclock->tag.myLock;
3892  LockInstanceData *instance;
3893 
3894  if (data->nlocks >= data->maxlocks)
3895  {
3896  data->maxlocks += MaxBackends;
3897  data->locks = (LockInstanceData *)
3898  repalloc(data->locks, sizeof(LockInstanceData) * data->maxlocks);
3899  }
3900 
3901  instance = &data->locks[data->nlocks];
3902  memcpy(&instance->locktag, &lock->tag, sizeof(LOCKTAG));
3903  instance->holdMask = proclock->holdMask;
3904  if (proc->waitLock == lock)
3905  instance->waitLockMode = proc->waitLockMode;
3906  else
3907  instance->waitLockMode = NoLock;
3908  instance->vxid.procNumber = proc->vxid.procNumber;
3909  instance->vxid.localTransactionId = proc->vxid.lxid;
3910  instance->pid = proc->pid;
3911  instance->leaderPid = proclock->groupLeader->pid;
3912  instance->fastpath = false;
3913  data->nlocks++;
3914  }
3915 
3916  /* Enlarge waiter_pids[] if it's too small to hold all wait queue PIDs */
3917  waitQueue = &(theLock->waitProcs);
3918  queue_size = dclist_count(waitQueue);
3919 
3920  if (queue_size > data->maxpids - data->npids)
3921  {
3922  data->maxpids = Max(data->maxpids + MaxBackends,
3923  data->npids + queue_size);
3924  data->waiter_pids = (int *) repalloc(data->waiter_pids,
3925  sizeof(int) * data->maxpids);
3926  }
3927 
3928  /* Collect PIDs from the lock's wait queue, stopping at blocked_proc */
3929  dclist_foreach(proc_iter, waitQueue)
3930  {
3931  PGPROC *queued_proc = dlist_container(PGPROC, links, proc_iter.cur);
3932 
3933  if (queued_proc == blocked_proc)
3934  break;
3935  data->waiter_pids[data->npids++] = queued_proc->pid;
3936  queued_proc = (PGPROC *) queued_proc->links.next;
3937  }
3938 
3939  bproc->num_locks = data->nlocks - bproc->first_lock;
3940  bproc->num_waiters = data->npids - bproc->first_waiter;
3941 }
3942 
3943 /*
3944  * Returns a list of currently held AccessExclusiveLocks, for use by
3945  * LogStandbySnapshot(). The result is a palloc'd array,
3946  * with the number of elements returned into *nlocks.
3947  *
3948  * XXX This currently takes a lock on all partitions of the lock table,
3949  * but it's possible to do better. By reference counting locks and storing
3950  * the value in the ProcArray entry for each backend we could tell if any
3951  * locks need recording without having to acquire the partition locks and
3952  * scan the lock table. Whether that's worth the additional overhead
3953  * is pretty dubious though.
3954  */
3957 {
3958  xl_standby_lock *accessExclusiveLocks;
3959  PROCLOCK *proclock;
3960  HASH_SEQ_STATUS seqstat;
3961  int i;
3962  int index;
3963  int els;
3964 
3965  /*
3966  * Acquire lock on the entire shared lock data structure.
3967  *
3968  * Must grab LWLocks in partition-number order to avoid LWLock deadlock.
3969  */
3970  for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
3972 
3973  /* Now we can safely count the number of proclocks */
3975 
3976  /*
3977  * Allocating enough space for all locks in the lock table is overkill,
3978  * but it's more convenient and faster than having to enlarge the array.
3979  */
3980  accessExclusiveLocks = palloc(els * sizeof(xl_standby_lock));
3981 
3982  /* Now scan the tables to copy the data */
3984 
3985  /*
3986  * If lock is a currently granted AccessExclusiveLock then it will have
3987  * just one proclock holder, so locks are never accessed twice in this
3988  * particular case. Don't copy this code for use elsewhere because in the
3989  * general case this will give you duplicate locks when looking at
3990  * non-exclusive lock types.
3991  */
3992  index = 0;
3993  while ((proclock = (PROCLOCK *) hash_seq_search(&seqstat)))
3994  {
3995  /* make sure this definition matches the one used in LockAcquire */
3996  if ((proclock->holdMask & LOCKBIT_ON(AccessExclusiveLock)) &&
3997  proclock->tag.myLock->tag.locktag_type == LOCKTAG_RELATION)
3998  {
3999  PGPROC *proc = proclock->tag.myProc;
4000  LOCK *lock = proclock->tag.myLock;
4001  TransactionId xid = proc->xid;
4002 
4003  /*
4004  * Don't record locks for transactions if we know they have
4005  * already issued their WAL record for commit but not yet released
4006  * lock. It is still possible that we see locks held by already
4007  * complete transactions, if they haven't yet zeroed their xids.
4008  */
4009  if (!TransactionIdIsValid(xid))
4010  continue;
4011 
4012  accessExclusiveLocks[index].xid = xid;
4013  accessExclusiveLocks[index].dbOid = lock->tag.locktag_field1;
4014  accessExclusiveLocks[index].relOid = lock->tag.locktag_field2;
4015 
4016  index++;
4017  }
4018  }
4019 
4020  Assert(index <= els);
4021 
4022  /*
4023  * And release locks. We do this in reverse order for two reasons: (1)
4024  * Anyone else who needs more than one of the locks will be trying to lock
4025  * them in increasing order; we don't want to release the other process
4026  * until it can get all the locks it needs. (2) This avoids O(N^2)
4027  * behavior inside LWLockRelease.
4028  */
4029  for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
4031 
4032  *nlocks = index;
4033  return accessExclusiveLocks;
4034 }
4035 
4036 /* Provide the textual name of any lock mode */
4037 const char *
4039 {
4040  Assert(lockmethodid > 0 && lockmethodid < lengthof(LockMethods));
4041  Assert(mode > 0 && mode <= LockMethods[lockmethodid]->numLockModes);
4042  return LockMethods[lockmethodid]->lockModeNames[mode];
4043 }
4044 
4045 #ifdef LOCK_DEBUG
4046 /*
4047  * Dump all locks in the given proc's myProcLocks lists.
4048  *
4049  * Caller is responsible for having acquired appropriate LWLocks.
4050  */
4051 void
4052 DumpLocks(PGPROC *proc)
4053 {
4054  int i;
4055 
4056  if (proc == NULL)
4057  return;
4058 
4059  if (proc->waitLock)
4060  LOCK_PRINT("DumpLocks: waiting on", proc->waitLock, 0);
4061 
4062  for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
4063  {
4064  dlist_head *procLocks = &proc->myProcLocks[i];
4065  dlist_iter iter;
4066 
4067  dlist_foreach(iter, procLocks)
4068  {
4069  PROCLOCK *proclock = dlist_container(PROCLOCK, procLink, iter.cur);
4070  LOCK *lock = proclock->tag.myLock;
4071 
4072  Assert(proclock->tag.myProc == proc);
4073  PROCLOCK_PRINT("DumpLocks", proclock);
4074  LOCK_PRINT("DumpLocks", lock, 0);
4075  }
4076  }
4077 }
4078 
4079 /*
4080  * Dump all lmgr locks.
4081  *
4082  * Caller is responsible for having acquired appropriate LWLocks.
4083  */
4084 void
4085 DumpAllLocks(void)
4086 {
4087  PGPROC *proc;
4088  PROCLOCK *proclock;
4089  LOCK *lock;
4090  HASH_SEQ_STATUS status;
4091 
4092  proc = MyProc;
4093 
4094  if (proc && proc->waitLock)
4095  LOCK_PRINT("DumpAllLocks: waiting on", proc->waitLock, 0);
4096 
4098 
4099  while ((proclock = (PROCLOCK *) hash_seq_search(&status)) != NULL)
4100  {
4101  PROCLOCK_PRINT("DumpAllLocks", proclock);
4102 
4103  lock = proclock->tag.myLock;
4104  if (lock)
4105  LOCK_PRINT("DumpAllLocks", lock, 0);
4106  else
4107  elog(LOG, "DumpAllLocks: proclock->tag.myLock = NULL");
4108  }
4109 }
4110 #endif /* LOCK_DEBUG */
4111 
4112 /*
4113  * LOCK 2PC resource manager's routines
4114  */
4115 
4116 /*
4117  * Re-acquire a lock belonging to a transaction that was prepared.
4118  *
4119  * Because this function is run at db startup, re-acquiring the locks should
4120  * never conflict with running transactions because there are none. We
4121  * assume that the lock state represented by the stored 2PC files is legal.
4122  *
4123  * When switching from Hot Standby mode to normal operation, the locks will
4124  * be already held by the startup process. The locks are acquired for the new
4125  * procs without checking for conflicts, so we don't get a conflict between the
4126  * startup process and the dummy procs, even though we will momentarily have
4127  * a situation where two procs are holding the same AccessExclusiveLock,
4128  * which isn't normally possible because the conflict. If we're in standby
4129  * mode, but a recovery snapshot hasn't been established yet, it's possible
4130  * that some but not all of the locks are already held by the startup process.
4131  *
4132  * This approach is simple, but also a bit dangerous, because if there isn't
4133  * enough shared memory to acquire the locks, an error will be thrown, which
4134  * is promoted to FATAL and recovery will abort, bringing down postmaster.
4135  * A safer approach would be to transfer the locks like we do in
4136  * AtPrepare_Locks, but then again, in hot standby mode it's possible for
4137  * read-only backends to use up all the shared lock memory anyway, so that
4138  * replaying the WAL record that needs to acquire a lock will throw an error
4139  * and PANIC anyway.
4140  */
4141 void
4143  void *recdata, uint32 len)
4144 {
4145  TwoPhaseLockRecord *rec = (TwoPhaseLockRecord *) recdata;
4146  PGPROC *proc = TwoPhaseGetDummyProc(xid, false);
4147  LOCKTAG *locktag;
4148  LOCKMODE lockmode;
4149  LOCKMETHODID lockmethodid;
4150  LOCK *lock;
4151  PROCLOCK *proclock;
4152  PROCLOCKTAG proclocktag;
4153  bool found;
4154  uint32 hashcode;
4155  uint32 proclock_hashcode;
4156  int partition;
4157  LWLock *partitionLock;
4158  LockMethod lockMethodTable;
4159 
4160  Assert(len == sizeof(TwoPhaseLockRecord));
4161  locktag = &rec->locktag;
4162  lockmode = rec->lockmode;
4163  lockmethodid = locktag->locktag_lockmethodid;
4164 
4165  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
4166  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
4167  lockMethodTable = LockMethods[lockmethodid];
4168 
4169  hashcode = LockTagHashCode(locktag);
4170  partition = LockHashPartition(hashcode);
4171  partitionLock = LockHashPartitionLock(hashcode);
4172 
4173  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
4174 
4175  /*
4176  * Find or create a lock with this tag.
4177  */
4179  locktag,
4180  hashcode,
4182  &found);
4183  if (!lock)
4184  {
4185  LWLockRelease(partitionLock);
4186  ereport(ERROR,
4187  (errcode(ERRCODE_OUT_OF_MEMORY),
4188  errmsg("out of shared memory"),
4189  errhint("You might need to increase %s.", "max_locks_per_transaction")));
4190  }
4191 
4192  /*
4193  * if it's a new lock object, initialize it
4194  */
4195  if (!found)
4196  {
4197  lock->grantMask = 0;
4198  lock->waitMask = 0;
4199  dlist_init(&lock->procLocks);
4200  dclist_init(&lock->waitProcs);
4201  lock->nRequested = 0;
4202  lock->nGranted = 0;
4203  MemSet(lock->requested, 0, sizeof(int) * MAX_LOCKMODES);
4204  MemSet(lock->granted, 0, sizeof(int) * MAX_LOCKMODES);
4205  LOCK_PRINT("lock_twophase_recover: new", lock, lockmode);
4206  }
4207  else
4208  {
4209  LOCK_PRINT("lock_twophase_recover: found", lock, lockmode);
4210  Assert((lock->nRequested >= 0) && (lock->requested[lockmode] >= 0));
4211  Assert((lock->nGranted >= 0) && (lock->granted[lockmode] >= 0));
4212  Assert(lock->nGranted <= lock->nRequested);
4213  }
4214 
4215  /*
4216  * Create the hash key for the proclock table.
4217  */
4218  proclocktag.myLock = lock;
4219  proclocktag.myProc = proc;
4220 
4221  proclock_hashcode = ProcLockHashCode(&proclocktag, hashcode);
4222 
4223  /*
4224  * Find or create a proclock entry with this tag
4225  */
4227  &proclocktag,
4228  proclock_hashcode,
4230  &found);
4231  if (!proclock)
4232  {
4233  /* Oops, not enough shmem for the proclock */
4234  if (lock->nRequested == 0)
4235  {
4236  /*
4237  * There are no other requestors of this lock, so garbage-collect
4238  * the lock object. We *must* do this to avoid a permanent leak
4239  * of shared memory, because there won't be anything to cause
4240  * anyone to release the lock object later.
4241  */
4242  Assert(dlist_is_empty(&lock->procLocks));
4244  &(lock->tag),
4245  hashcode,
4246  HASH_REMOVE,
4247  NULL))
4248  elog(PANIC, "lock table corrupted");
4249  }
4250  LWLockRelease(partitionLock);
4251  ereport(ERROR,
4252  (errcode(ERRCODE_OUT_OF_MEMORY),
4253  errmsg("out of shared memory"),
4254  errhint("You might need to increase %s.", "max_locks_per_transaction")));
4255  }
4256 
4257  /*
4258  * If new, initialize the new entry
4259  */
4260  if (!found)
4261  {
4262  Assert(proc->lockGroupLeader == NULL);
4263  proclock->groupLeader = proc;
4264  proclock->holdMask = 0;
4265  proclock->releaseMask = 0;
4266  /* Add proclock to appropriate lists */
4267  dlist_push_tail(&lock->procLocks, &proclock->lockLink);
4268  dlist_push_tail(&proc->myProcLocks[partition],
4269  &proclock->procLink);
4270  PROCLOCK_PRINT("lock_twophase_recover: new", proclock);
4271  }
4272  else
4273  {
4274  PROCLOCK_PRINT("lock_twophase_recover: found", proclock);
4275  Assert((proclock->holdMask & ~lock->grantMask) == 0);
4276  }
4277 
4278  /*
4279  * lock->nRequested and lock->requested[] count the total number of
4280  * requests, whether granted or waiting, so increment those immediately.
4281  */
4282  lock->nRequested++;
4283  lock->requested[lockmode]++;
4284  Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
4285 
4286  /*
4287  * We shouldn't already hold the desired lock.
4288  */
4289  if (proclock->holdMask & LOCKBIT_ON(lockmode))
4290  elog(ERROR, "lock %s on object %u/%u/%u is already held",
4291  lockMethodTable->lockModeNames[lockmode],
4292  lock->tag.locktag_field1, lock->tag.locktag_field2,
4293  lock->tag.locktag_field3);
4294 
4295  /*
4296  * We ignore any possible conflicts and just grant ourselves the lock. Not
4297  * only because we don't bother, but also to avoid deadlocks when
4298  * switching from standby to normal mode. See function comment.
4299  */
4300  GrantLock(lock, proclock, lockmode);
4301 
4302  /*
4303  * Bump strong lock count, to make sure any fast-path lock requests won't
4304  * be granted without consulting the primary lock table.
4305  */
4306  if (ConflictsWithRelationFastPath(&lock->tag, lockmode))
4307  {
4308  uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
4309 
4311  FastPathStrongRelationLocks->count[fasthashcode]++;
4313  }
4314 
4315  LWLockRelease(partitionLock);
4316 }
4317 
4318 /*
4319  * Re-acquire a lock belonging to a transaction that was prepared, when
4320  * starting up into hot standby mode.
4321  */
4322 void
4324  void *recdata, uint32 len)
4325 {
4326  TwoPhaseLockRecord *rec = (TwoPhaseLockRecord *) recdata;
4327  LOCKTAG *locktag;
4328  LOCKMODE lockmode;
4329  LOCKMETHODID lockmethodid;
4330 
4331  Assert(len == sizeof(TwoPhaseLockRecord));
4332  locktag = &rec->locktag;
4333  lockmode = rec->lockmode;
4334  lockmethodid = locktag->locktag_lockmethodid;
4335 
4336  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
4337  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
4338 
4339  if (lockmode == AccessExclusiveLock &&
4340  locktag->locktag_type == LOCKTAG_RELATION)
4341  {
4343  locktag->locktag_field1 /* dboid */ ,
4344  locktag->locktag_field2 /* reloid */ );
4345  }
4346 }
4347 
4348 
4349 /*
4350  * 2PC processing routine for COMMIT PREPARED case.
4351  *
4352  * Find and release the lock indicated by the 2PC record.
4353  */
4354 void
4356  void *recdata, uint32 len)
4357 {
4358  TwoPhaseLockRecord *rec = (TwoPhaseLockRecord *) recdata;
4359  PGPROC *proc = TwoPhaseGetDummyProc(xid, true);
4360  LOCKTAG *locktag;
4361  LOCKMETHODID lockmethodid;
4362  LockMethod lockMethodTable;
4363 
4364  Assert(len == sizeof(TwoPhaseLockRecord));
4365  locktag = &rec->locktag;
4366  lockmethodid = locktag->locktag_lockmethodid;
4367 
4368  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
4369  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
4370  lockMethodTable = LockMethods[lockmethodid];
4371 
4372  LockRefindAndRelease(lockMethodTable, proc, locktag, rec->lockmode, true);
4373 }
4374 
4375 /*
4376  * 2PC processing routine for ROLLBACK PREPARED case.
4377  *
4378  * This is actually just the same as the COMMIT case.
4379  */
4380 void
4382  void *recdata, uint32 len)
4383 {
4384  lock_twophase_postcommit(xid, info, recdata, len);
4385 }
4386 
4387 /*
4388  * VirtualXactLockTableInsert
4389  *
4390  * Take vxid lock via the fast-path. There can't be any pre-existing
4391  * lockers, as we haven't advertised this vxid via the ProcArray yet.
4392  *
4393  * Since MyProc->fpLocalTransactionId will normally contain the same data
4394  * as MyProc->vxid.lxid, you might wonder if we really need both. The
4395  * difference is that MyProc->vxid.lxid is set and cleared unlocked, and
4396  * examined by procarray.c, while fpLocalTransactionId is protected by
4397  * fpInfoLock and is used only by the locking subsystem. Doing it this
4398  * way makes it easier to verify that there are no funny race conditions.
4399  *
4400  * We don't bother recording this lock in the local lock table, since it's
4401  * only ever released at the end of a transaction. Instead,
4402  * LockReleaseAll() calls VirtualXactLockTableCleanup().
4403  */
4404 void
4406 {
4408 
4410 
4413  Assert(MyProc->fpVXIDLock == false);
4414 
4415  MyProc->fpVXIDLock = true;
4417 
4419 }
4420 
4421 /*
4422  * VirtualXactLockTableCleanup
4423  *
4424  * Check whether a VXID lock has been materialized; if so, release it,
4425  * unblocking waiters.
4426  */
4427 void
4429 {
4430  bool fastpath;
4431  LocalTransactionId lxid;
4432 
4434 
4435  /*
4436  * Clean up shared memory state.
4437  */
4439 
4440  fastpath = MyProc->fpVXIDLock;
4441  lxid = MyProc->fpLocalTransactionId;
4442  MyProc->fpVXIDLock = false;
4444 
4446 
4447  /*
4448  * If fpVXIDLock has been cleared without touching fpLocalTransactionId,
4449  * that means someone transferred the lock to the main lock table.
4450  */
4451  if (!fastpath && LocalTransactionIdIsValid(lxid))
4452  {
4453  VirtualTransactionId vxid;
4454  LOCKTAG locktag;
4455 
4456  vxid.procNumber = MyProcNumber;
4457  vxid.localTransactionId = lxid;
4458  SET_LOCKTAG_VIRTUALTRANSACTION(locktag, vxid);
4459 
4461  &locktag, ExclusiveLock, false);
4462  }
4463 }
4464 
4465 /*
4466  * XactLockForVirtualXact
4467  *
4468  * If TransactionIdIsValid(xid), this is essentially XactLockTableWait(xid,
4469  * NULL, NULL, XLTW_None) or ConditionalXactLockTableWait(xid). Unlike those
4470  * functions, it assumes "xid" is never a subtransaction and that "xid" is
4471  * prepared, committed, or aborted.
4472  *
4473  * If !TransactionIdIsValid(xid), this locks every prepared XID having been
4474  * known as "vxid" before its PREPARE TRANSACTION.
4475  */
4476 static bool
4478  TransactionId xid, bool wait)
4479 {
4480  bool more = false;
4481 
4482  /* There is no point to wait for 2PCs if you have no 2PCs. */
4483  if (max_prepared_xacts == 0)
4484  return true;
4485 
4486  do
4487  {
4488  LockAcquireResult lar;
4489  LOCKTAG tag;
4490 
4491  /* Clear state from previous iterations. */
4492  if (more)
4493  {
4494  xid = InvalidTransactionId;
4495  more = false;
4496  }
4497 
4498  /* If we have no xid, try to find one. */
4499  if (!TransactionIdIsValid(xid))
4500  xid = TwoPhaseGetXidByVirtualXID(vxid, &more);
4501  if (!TransactionIdIsValid(xid))
4502  {
4503  Assert(!more);
4504  return true;
4505  }
4506 
4507  /* Check or wait for XID completion. */
4508  SET_LOCKTAG_TRANSACTION(tag, xid);
4509  lar = LockAcquire(&tag, ShareLock, false, !wait);
4510  if (lar == LOCKACQUIRE_NOT_AVAIL)
4511  return false;
4512  LockRelease(&tag, ShareLock, false);
4513  } while (more);
4514 
4515  return true;
4516 }
4517 
4518 /*
4519  * VirtualXactLock
4520  *
4521  * If wait = true, wait as long as the given VXID or any XID acquired by the
4522  * same transaction is still running. Then, return true.
4523  *
4524  * If wait = false, just check whether that VXID or one of those XIDs is still
4525  * running, and return true or false.
4526  */
4527 bool
4529 {
4530  LOCKTAG tag;
4531  PGPROC *proc;
4533 
4535 
4537  /* no vxid lock; localTransactionId is a normal, locked XID */
4538  return XactLockForVirtualXact(vxid, vxid.localTransactionId, wait);
4539 
4540  SET_LOCKTAG_VIRTUALTRANSACTION(tag, vxid);
4541 
4542  /*
4543  * If a lock table entry must be made, this is the PGPROC on whose behalf
4544  * it must be done. Note that the transaction might end or the PGPROC
4545  * might be reassigned to a new backend before we get around to examining
4546  * it, but it doesn't matter. If we find upon examination that the
4547  * relevant lxid is no longer running here, that's enough to prove that
4548  * it's no longer running anywhere.
4549  */
4550  proc = ProcNumberGetProc(vxid.procNumber);
4551  if (proc == NULL)
4552  return XactLockForVirtualXact(vxid, InvalidTransactionId, wait);
4553 
4554  /*
4555  * We must acquire this lock before checking the procNumber and lxid
4556  * against the ones we're waiting for. The target backend will only set
4557  * or clear lxid while holding this lock.
4558  */
4560 
4561  if (proc->vxid.procNumber != vxid.procNumber
4562  || proc->fpLocalTransactionId != vxid.localTransactionId)
4563  {
4564  /* VXID ended */
4565  LWLockRelease(&proc->fpInfoLock);
4566  return XactLockForVirtualXact(vxid, InvalidTransactionId, wait);
4567  }
4568 
4569  /*
4570  * If we aren't asked to wait, there's no need to set up a lock table
4571  * entry. The transaction is still in progress, so just return false.
4572  */
4573  if (!wait)
4574  {
4575  LWLockRelease(&proc->fpInfoLock);
4576  return false;
4577  }
4578 
4579  /*
4580  * OK, we're going to need to sleep on the VXID. But first, we must set
4581  * up the primary lock table entry, if needed (ie, convert the proc's
4582  * fast-path lock on its VXID to a regular lock).
4583  */
4584  if (proc->fpVXIDLock)
4585  {
4586  PROCLOCK *proclock;
4587  uint32 hashcode;
4588  LWLock *partitionLock;
4589 
4590  hashcode = LockTagHashCode(&tag);
4591 
4592  partitionLock = LockHashPartitionLock(hashcode);
4593  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
4594 
4596  &tag, hashcode, ExclusiveLock);
4597  if (!proclock)
4598  {
4599  LWLockRelease(partitionLock);
4600  LWLockRelease(&proc->fpInfoLock);
4601  ereport(ERROR,
4602  (errcode(ERRCODE_OUT_OF_MEMORY),
4603  errmsg("out of shared memory"),
4604  errhint("You might need to increase %s.", "max_locks_per_transaction")));
4605  }
4606  GrantLock(proclock->tag.myLock, proclock, ExclusiveLock);
4607 
4608  LWLockRelease(partitionLock);
4609 
4610  proc->fpVXIDLock = false;
4611  }
4612 
4613  /*
4614  * If the proc has an XID now, we'll avoid a TwoPhaseGetXidByVirtualXID()
4615  * search. The proc might have assigned this XID but not yet locked it,
4616  * in which case the proc will lock this XID before releasing the VXID.
4617  * The fpInfoLock critical section excludes VirtualXactLockTableCleanup(),
4618  * so we won't save an XID of a different VXID. It doesn't matter whether
4619  * we save this before or after setting up the primary lock table entry.
4620  */
4621  xid = proc->xid;
4622 
4623  /* Done with proc->fpLockBits */
4624  LWLockRelease(&proc->fpInfoLock);
4625 
4626  /* Time to wait. */
4627  (void) LockAcquire(&tag, ShareLock, false, false);
4628 
4629  LockRelease(&tag, ShareLock, false);
4630  return XactLockForVirtualXact(vxid, xid, wait);
4631 }
4632 
4633 /*
4634  * LockWaiterCount
4635  *
4636  * Find the number of lock requester on this locktag
4637  */
4638 int
4639 LockWaiterCount(const LOCKTAG *locktag)
4640 {
4641  LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
4642  LOCK *lock;
4643  bool found;
4644  uint32 hashcode;
4645  LWLock *partitionLock;
4646  int waiters = 0;
4647 
4648  if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
4649  elog(ERROR, "unrecognized lock method: %d", lockmethodid);
4650 
4651  hashcode = LockTagHashCode(locktag);
4652  partitionLock = LockHashPartitionLock(hashcode);
4653  LWLockAcquire(partitionLock, LW_EXCLUSIVE);
4654 
4656  locktag,
4657  hashcode,
4658  HASH_FIND,
4659  &found);
4660  if (found)
4661  {
4662  Assert(lock != NULL);
4663  waiters = lock->nRequested;
4664  }
4665  LWLockRelease(partitionLock);
4666 
4667  return waiters;
4668 }
static uint64 pg_atomic_read_u64(volatile pg_atomic_uint64 *ptr)
Definition: atomics.h:462
unsigned short uint16
Definition: c.h:505
unsigned int uint32
Definition: c.h:506
#define Max(x, y)
Definition: c.h:998
#define Assert(condition)
Definition: c.h:858
#define lengthof(array)
Definition: c.h:788
uint32 LocalTransactionId
Definition: c.h:654
#define MemSet(start, val, len)
Definition: c.h:1020
uint32 TransactionId
Definition: c.h:652
size_t Size
Definition: c.h:605
int64 TimestampTz
Definition: timestamp.h:39
void DeadLockReport(void)
Definition: deadlock.c:1072
void hash_destroy(HTAB *hashp)
Definition: dynahash.c:865
void * hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:955
HTAB * hash_create(const char *tabname, long nelem, const HASHCTL *info, int flags)
Definition: dynahash.c:352
long hash_get_num_entries(HTAB *hashp)
Definition: dynahash.c:1341
Size hash_estimate_size(long num_entries, Size entrysize)
Definition: dynahash.c:783
bool hash_update_hash_key(HTAB *hashp, void *existingEntry, const void *newKeyPtr)
Definition: dynahash.c:1145
uint32 get_hash_value(HTAB *hashp, const void *keyPtr)
Definition: dynahash.c:911
void * hash_search_with_hash_value(HTAB *hashp, const void *keyPtr, uint32 hashvalue, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:968
void * hash_seq_search(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1395
void hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
Definition: dynahash.c:1385
int errhint(const char *fmt,...)
Definition: elog.c:1319
int errcode(int sqlerrcode)
Definition: elog.c:859
int errmsg(const char *fmt,...)
Definition: elog.c:1072
#define LOG
Definition: elog.h:31
#define PG_RE_THROW()
Definition: elog.h:411
#define PG_TRY(...)
Definition: elog.h:370
#define WARNING
Definition: elog.h:36
#define PG_END_TRY(...)
Definition: elog.h:395
#define PANIC
Definition: elog.h:42
#define ERROR
Definition: elog.h:39
#define PG_CATCH(...)
Definition: elog.h:380
#define elog(elevel,...)
Definition: elog.h:224
#define ereport(elevel,...)
Definition: elog.h:149
ProcNumber MyProcNumber
Definition: globals.c:87
int MaxBackends
Definition: globals.c:143
@ HASH_FIND
Definition: hsearch.h:113
@ HASH_REMOVE
Definition: hsearch.h:115
@ HASH_ENTER
Definition: hsearch.h:114
@ HASH_ENTER_NULL
Definition: hsearch.h:116
#define HASH_CONTEXT
Definition: hsearch.h:102
#define HASH_ELEM
Definition: hsearch.h:95
#define HASH_FUNCTION
Definition: hsearch.h:98
#define HASH_BLOBS
Definition: hsearch.h:97
#define HASH_PARTITION
Definition: hsearch.h:92
#define dlist_foreach(iter, lhead)
Definition: ilist.h:623
static void dlist_init(dlist_head *head)
Definition: ilist.h:314
static void dlist_delete(dlist_node *node)
Definition: ilist.h:405
static uint32 dclist_count(const dclist_head *head)
Definition: ilist.h:932
static bool dclist_is_empty(const dclist_head *head)
Definition: ilist.h:682
#define dlist_foreach_modify(iter, lhead)
Definition: ilist.h:640
static bool dlist_is_empty(const dlist_head *head)
Definition: ilist.h:336
static void dlist_push_tail(dlist_head *head, dlist_node *node)
Definition: ilist.h:364
static void dclist_delete_from_thoroughly(dclist_head *head, dlist_node *node)
Definition: ilist.h:776
static void dclist_init(dclist_head *head)
Definition: ilist.h:671
#define dlist_container(type, membername, ptr)
Definition: ilist.h:593
#define dclist_foreach(iter, lhead)
Definition: ilist.h:970
int i
Definition: isn.c:73
static bool XactLockForVirtualXact(VirtualTransactionId vxid, TransactionId xid, bool wait)
Definition: lock.c:4477
LockAcquireResult LockAcquire(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock, bool dontWait)
Definition: lock.c:734
static LOCALLOCK * awaitedLock
Definition: lock.c:274
static void RemoveLocalLock(LOCALLOCK *locallock)
Definition: lock.c:1354
LockAcquireResult LockAcquireExtended(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock, bool dontWait, bool reportMemoryError, LOCALLOCK **locallockp)
Definition: lock.c:758
static void LockReassignOwner(LOCALLOCK *locallock, ResourceOwner parent)
Definition: lock.c:2567
VirtualTransactionId * GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode, int *countp)
Definition: lock.c:2872
static bool Dummy_trace
Definition: lock.c:121
static const char *const lock_mode_names[]
Definition: lock.c:107
#define LOCK_PRINT(where, lock, type)
Definition: lock.c:351
bool DoLockModesConflict(LOCKMODE mode1, LOCKMODE mode2)
Definition: lock.c:570
static PROCLOCK * SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc, const LOCKTAG *locktag, uint32 hashcode, LOCKMODE lockmode)
Definition: lock.c:1161
static PROCLOCK * FastPathGetRelationLockEntry(LOCALLOCK *locallock)
Definition: lock.c:2768
void VirtualXactLockTableInsert(VirtualTransactionId vxid)
Definition: lock.c:4405
#define NLOCKENTS()
Definition: lock.c:55
#define FastPathStrongLockHashPartition(hashcode)
Definition: lock.c:249
static uint32 ProcLockHashCode(const PROCLOCKTAG *proclocktag, uint32 hashcode)
Definition: lock.c:552
xl_standby_lock * GetRunningTransactionLocks(int *nlocks)
Definition: lock.c:3956
#define FAST_PATH_CHECK_LOCKMODE(proc, n, l)
Definition: lock.c:202
void GrantAwaitedLock(void)
Definition: lock.c:1767
int LockWaiterCount(const LOCKTAG *locktag)
Definition: lock.c:4639
bool LockHeldByMe(const LOCKTAG *locktag, LOCKMODE lockmode)
Definition: lock.c:585
void AtPrepare_Locks(void)
Definition: lock.c:3272
bool LockRelease(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock)
Definition: lock.c:1942
void lock_twophase_postcommit(TransactionId xid, uint16 info, void *recdata, uint32 len)
Definition: lock.c:4355
#define FAST_PATH_LOCKNUMBER_OFFSET
Definition: lock.c:189
void GrantLock(LOCK *lock, PROCLOCK *proclock, LOCKMODE lockmode)
Definition: lock.c:1536
void VirtualXactLockTableCleanup(void)
Definition: lock.c:4428
BlockedProcsData * GetBlockerStatusData(int blocked_pid)
Definition: lock.c:3781
bool VirtualXactLock(VirtualTransactionId vxid, bool wait)
Definition: lock.c:4528
static volatile FastPathStrongRelationLockData * FastPathStrongRelationLocks
Definition: lock.c:258
void RemoveFromWaitQueue(PGPROC *proc, uint32 hashcode)
Definition: lock.c:1886
void LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks)
Definition: lock.c:2147
static void CheckAndSetLockHeld(LOCALLOCK *locallock, bool acquired)
Definition: lock.c:1342
void InitLocks(void)
Definition: lock.c:392
#define ConflictsWithRelationFastPath(locktag, mode)
Definition: lock.c:219
static bool FastPathTransferRelationLocks(LockMethod lockMethodTable, const LOCKTAG *locktag, uint32 hashcode)
Definition: lock.c:2680
static HTAB * LockMethodLocalHash
Definition: lock.c:269
void LockReassignCurrentOwner(LOCALLOCK **locallocks, int nlocks)
Definition: lock.c:2537
static bool UnGrantLock(LOCK *lock, LOCKMODE lockmode, PROCLOCK *proclock, LockMethod lockMethodTable)
Definition: lock.c:1559
static void WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner, bool dontWait)
Definition: lock.c:1796
#define FAST_PATH_SET_LOCKMODE(proc, n, l)
Definition: lock.c:198
#define PROCLOCK_PRINT(where, proclockP)
Definition: lock.c:352
LockData * GetLockStatusData(void)
Definition: lock.c:3589
static void CleanUpLock(LOCK *lock, PROCLOCK *proclock, LockMethod lockMethodTable, uint32 hashcode, bool wakeupNeeded)
Definition: lock.c:1616
static uint32 proclock_hash(const void *key, Size keysize)
Definition: lock.c:521
static bool FastPathUnGrantRelationLock(Oid relid, LOCKMODE lockmode)
Definition: lock.c:2650
void AbortStrongLockAcquire(void)
Definition: lock.c:1738
static bool FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode)
Definition: lock.c:2613
static HTAB * LockMethodLockHash
Definition: lock.c:267
static ResourceOwner awaitedOwner
Definition: lock.c:275
void lock_twophase_postabort(TransactionId xid, uint16 info, void *recdata, uint32 len)
Definition: lock.c:4381
bool LockHasWaiters(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock)
Definition: lock.c:621
static void GetSingleProcBlockerStatusData(PGPROC *blocked_proc, BlockedProcsData *data)
Definition: lock.c:3861
#define FAST_PATH_CLEAR_LOCKMODE(proc, n, l)
Definition: lock.c:200
int max_locks_per_xact
Definition: lock.c:53
static const LockMethod LockMethods[]
Definition: lock.c:149
void lock_twophase_standby_recover(TransactionId xid, uint16 info, void *recdata, uint32 len)
Definition: lock.c:4323
void LockReleaseCurrentOwner(LOCALLOCK **locallocks, int nlocks)
Definition: lock.c:2442
void lock_twophase_recover(TransactionId xid, uint16 info, void *recdata, uint32 len)
Definition: lock.c:4142
void LockReleaseSession(LOCKMETHODID lockmethodid)
Definition: lock.c:2412
Size LockShmemSize(void)
Definition: lock.c:3552
void MarkLockClear(LOCALLOCK *locallock)
Definition: lock.c:1780
static bool IsRelationExtensionLockHeld PG_USED_FOR_ASSERTS_ONLY
Definition: lock.c:185
const char * GetLockmodeName(LOCKMETHODID lockmethodid, LOCKMODE mode)
Definition: lock.c:4038
static const LockMethodData default_lockmethod
Definition: lock.c:124
#define FAST_PATH_GET_BITS(proc, n)
Definition: lock.c:191
static LOCALLOCK * StrongLockInProgress
Definition: lock.c:273
#define FAST_PATH_BITS_PER_SLOT
Definition: lock.c:188
static const LockMethodData user_lockmethod
Definition: lock.c:135
static int FastPathLocalUseCount
Definition: lock.c:170
#define EligibleForRelationFastPath(locktag, mode)
Definition: lock.c:213
uint32 LockTagHashCode(const LOCKTAG *locktag)
Definition: lock.c:504
static void BeginStrongLockAcquire(LOCALLOCK *locallock, uint32 fasthashcode)
Definition: lock.c:1702
bool LockCheckConflicts(LockMethod lockMethodTable, LOCKMODE lockmode, LOCK *lock, PROCLOCK *proclock)
Definition: lock.c:1407
static void GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner)
Definition: lock.c:1670
static const LOCKMASK LockConflicts[]
Definition: lock.c:64
static void ReleaseLockIfHeld(LOCALLOCK *locallock, bool sessionLock)
Definition: lock.c:2477
LockMethod GetLocksMethodTable(const LOCK *lock)
Definition: lock.c:474
static void FinishStrongLockAcquire(void)
Definition: lock.c:1728
#define FAST_PATH_STRONG_LOCK_HASH_PARTITIONS
Definition: lock.c:247
void PostPrepare_Locks(TransactionId xid)
Definition: lock.c:3368
static void LockRefindAndRelease(LockMethod lockMethodTable, PGPROC *proc, LOCKTAG *locktag, LOCKMODE lockmode, bool decrement_strong_lock_count)
Definition: lock.c:3080
static void CheckForSessionAndXactLocks(void)
Definition: lock.c:3184
static HTAB * LockMethodProcLockHash
Definition: lock.c:268
struct TwoPhaseLockRecord TwoPhaseLockRecord
LockMethod GetLockTagsMethodTable(const LOCKTAG *locktag)
Definition: lock.c:486
uint16 LOCKMETHODID
Definition: lock.h:122
#define DEFAULT_LOCKMETHOD
Definition: lock.h:125
struct LOCALLOCK LOCALLOCK
#define LOCK_LOCKTAG(lock)
Definition: lock.h:325
struct LOCK LOCK
#define SET_LOCKTAG_VIRTUALTRANSACTION(locktag, vxid)
Definition: lock.h:235
struct PROCLOCK PROCLOCK
@ LOCKTAG_OBJECT
Definition: lock.h:145
@ LOCKTAG_RELATION_EXTEND
Definition: lock.h:138
@ LOCKTAG_RELATION
Definition: lock.h:137
@ LOCKTAG_VIRTUALTRANSACTION
Definition: lock.h:143
#define VirtualTransactionIdIsValid(vxid)
Definition: lock.h:67
#define LockHashPartitionLock(hashcode)
Definition: lock.h:526
#define GET_VXID_FROM_PGPROC(vxid_dst, proc)
Definition: lock.h:77
#define LOCK_LOCKMETHOD(lock)
Definition: lock.h:324
#define LOCKBIT_OFF(lockmode)
Definition: lock.h:85
#define LOCALLOCK_LOCKMETHOD(llock)
Definition: lock.h:443
#define InvalidLocalTransactionId
Definition: lock.h:65
#define SET_LOCKTAG_TRANSACTION(locktag, xid)
Definition: lock.h:226
struct LOCKTAG LOCKTAG
#define SET_LOCKTAG_RELATION(locktag, dboid, reloid)
Definition: lock.h:181
#define MAX_LOCKMODES
Definition: lock.h:82
struct PROCLOCKTAG PROCLOCKTAG
#define LOCKBIT_ON(lockmode)
Definition: lock.h:84
#define LocalTransactionIdIsValid(lxid)
Definition: lock.h:66
#define LOCALLOCK_LOCKTAG(llock)
Definition: lock.h:444
#define LockHashPartition(hashcode)
Definition: lock.h:524
#define VirtualTransactionIdEquals(vxid1, vxid2)
Definition: lock.h:71
struct LOCALLOCKTAG LOCALLOCKTAG
#define PROCLOCK_LOCKMETHOD(proclock)
Definition: lock.h:382
#define LockHashPartitionLockByIndex(i)
Definition: lock.h:529
LockAcquireResult
Definition: lock.h:500
@ LOCKACQUIRE_ALREADY_CLEAR
Definition: lock.h:504
@ LOCKACQUIRE_OK
Definition: lock.h:502
@ LOCKACQUIRE_ALREADY_HELD
Definition: lock.h:503
@ LOCKACQUIRE_NOT_AVAIL
Definition: lock.h:501
#define VirtualTransactionIdIsRecoveredPreparedXact(vxid)
Definition: lock.h:69
int LOCKMODE
Definition: lockdefs.h:26
#define NoLock
Definition: lockdefs.h:34
#define AccessExclusiveLock
Definition: lockdefs.h:43
#define ShareRowExclusiveLock
Definition: lockdefs.h:41
#define AccessShareLock
Definition: lockdefs.h:36
int LOCKMASK
Definition: lockdefs.h:25
#define ShareUpdateExclusiveLock
Definition: lockdefs.h:39
#define ExclusiveLock
Definition: lockdefs.h:42
#define RowShareLock
Definition: lockdefs.h:37
#define ShareLock
Definition: lockdefs.h:40
#define MaxLockMode
Definition: lockdefs.h:45
#define RowExclusiveLock
Definition: lockdefs.h:38
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1170
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1783
#define NUM_LOCK_PARTITIONS
Definition: lwlock.h:97
#define LOG2_NUM_LOCK_PARTITIONS
Definition: lwlock.h:96
@ LW_SHARED
Definition: lwlock.h:115
@ LW_EXCLUSIVE
Definition: lwlock.h:114
void pfree(void *pointer)
Definition: mcxt.c:1520
MemoryContext TopMemoryContext
Definition: mcxt.c:149
void * palloc0(Size size)
Definition: mcxt.c:1346
MemoryContext CurrentMemoryContext
Definition: mcxt.c:143
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1540
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:1180
void * palloc(Size size)
Definition: mcxt.c:1316
#define START_CRIT_SECTION()
Definition: miscadmin.h:149
#define END_CRIT_SECTION()
Definition: miscadmin.h:151
static PgChecksumMode mode
Definition: pg_checksums.c:56
const void size_t len
const void * data
static Datum PointerGetDatum(const void *X)
Definition: postgres.h:322
uintptr_t Datum
Definition: postgres.h:64
unsigned int Oid
Definition: postgres_ext.h:31
#define FP_LOCK_SLOTS_PER_BACKEND
Definition: proc.h:80
@ PROC_WAIT_STATUS_OK
Definition: proc.h:119
@ PROC_WAIT_STATUS_WAITING
Definition: proc.h:120
@ PROC_WAIT_STATUS_ERROR
Definition: proc.h:121
PGPROC * ProcNumberGetProc(ProcNumber procNumber)
Definition: procarray.c:3125
PGPROC * BackendPidGetProcWithLock(int pid)
Definition: procarray.c:3206
#define INVALID_PROC_NUMBER
Definition: procnumber.h:26
void set_ps_display_remove_suffix(void)
Definition: ps_status.c:421
void set_ps_display_suffix(const char *suffix)
Definition: ps_status.c:369
void ResourceOwnerRememberLock(ResourceOwner owner, LOCALLOCK *locallock)
Definition: resowner.c:1045
ResourceOwner ResourceOwnerGetParent(ResourceOwner owner)
Definition: resowner.c:888
ResourceOwner CurrentResourceOwner
Definition: resowner.c:165
void ResourceOwnerForgetLock(ResourceOwner owner, LOCALLOCK *locallock)
Definition: resowner.c:1065
int slock_t
Definition: s_lock.h:735
Size add_size(Size s1, Size s2)
Definition: shmem.c:493
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:387
HTAB * ShmemInitHash(const char *name, long init_size, long max_size, HASHCTL *infoP, int hash_flags)
Definition: shmem.c:332
static pg_noinline void Size size
Definition: slab.c:607
#define SpinLockInit(lock)
Definition: spin.h:60
#define SpinLockRelease(lock)
Definition: spin.h:64
#define SpinLockAcquire(lock)
Definition: spin.h:62
PGPROC * MyProc
Definition: proc.c:66
ProcWaitStatus ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable, bool dontWait)
Definition: proc.c:1066
void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
Definition: proc.c:1706
PROC_HDR * ProcGlobal
Definition: proc.c:78
void LogAccessExclusiveLockPrepare(void)
Definition: standby.c:1440
void StandbyAcquireAccessExclusiveLock(TransactionId xid, Oid dbOid, Oid relOid)
Definition: standby.c:985
void LogAccessExclusiveLock(Oid dbOid, Oid relOid)
Definition: standby.c:1423
int first_lock
Definition: lock.h:476
int first_waiter
Definition: lock.h:480
int num_waiters
Definition: lock.h:481
int num_locks
Definition: lock.h:477
uint32 count[FAST_PATH_STRONG_LOCK_HASH_PARTITIONS]
Definition: lock.c:255
Size keysize
Definition: hsearch.h:75
HashValueFunc hash
Definition: hsearch.h:78
Size entrysize
Definition: hsearch.h:76
MemoryContext hcxt
Definition: hsearch.h:86
long num_partitions
Definition: hsearch.h:68
Definition: dynahash.c:220
int64 nLocks
Definition: lock.h:423
struct ResourceOwnerData * owner
Definition: lock.h:422
LOCKTAG lock
Definition: lock.h:410
LOCKMODE mode
Definition: lock.h:411
LOCALLOCKOWNER * lockOwners
Definition: lock.h:438
uint32 hashcode
Definition: lock.h:432
int maxLockOwners
Definition: lock.h:437
LOCK * lock
Definition: lock.h:433
int64 nLocks
Definition: lock.h:435
int numLockOwners
Definition: lock.h:436
bool holdsStrongLockCount
Definition: lock.h:439
PROCLOCK * proclock
Definition: lock.h:434
LOCALLOCKTAG tag
Definition: lock.h:429
bool lockCleared
Definition: lock.h:440
Definition: lock.h:165
uint8 locktag_type
Definition: lock.h:170
uint32 locktag_field3
Definition: lock.h:168
uint32 locktag_field1
Definition: lock.h:166
uint8 locktag_lockmethodid
Definition: lock.h:171
uint16 locktag_field4
Definition: lock.h:169
uint32 locktag_field2
Definition: lock.h:167
Definition: lock.h:309
int nRequested
Definition: lock.h:319
LOCKTAG tag
Definition: lock.h:311
int requested[MAX_LOCKMODES]
Definition: lock.h:318
dclist_head waitProcs
Definition: lock.h:317
int granted[MAX_LOCKMODES]
Definition: lock.h:320
LOCKMASK grantMask
Definition: lock.h:314
LOCKMASK waitMask
Definition: lock.h:315
int nGranted
Definition: lock.h:321
dlist_head procLocks
Definition: lock.h:316
Definition: lwlock.h:42
Definition: lock.h:466
LOCKMASK holdMask
Definition: lock.h:455
LOCKMODE waitLockMode
Definition: lock.h:456
bool fastpath
Definition: lock.h:462
LOCKTAG locktag
Definition: lock.h:454
TimestampTz waitStart
Definition: lock.h:458
int leaderPid
Definition: lock.h:461
VirtualTransactionId vxid
Definition: lock.h:457
const bool * trace_flag
Definition: lock.h:113
const LOCKMASK * conflictTab
Definition: lock.h:111
const char *const * lockModeNames
Definition: lock.h:112
int numLockModes
Definition: lock.h:110
Definition: proc.h:157
LWLock fpInfoLock
Definition: proc.h:289
Oid fpRelId[FP_LOCK_SLOTS_PER_BACKEND]
Definition: proc.h:291
LocalTransactionId lxid
Definition: proc.h:196
PROCLOCK * waitProcLock
Definition: proc.h:229
dlist_head lockGroupMembers
Definition: proc.h:301
Oid databaseId
Definition: proc.h:203
pg_atomic_uint64 waitStart
Definition: proc.h:233
bool fpVXIDLock
Definition: proc.h:292
ProcNumber procNumber
Definition: proc.h:191
int pid
Definition: proc.h:178
LOCK * waitLock
Definition: proc.h:228
TransactionId xid
Definition: proc.h:168
LOCKMODE waitLockMode
Definition: proc.h:230
PGPROC * lockGroupLeader
Definition: proc.h:300
struct PGPROC::@117 vxid
LocalTransactionId fpLocalTransactionId
Definition: proc.h:293
LOCKMASK heldLocks
Definition: proc.h:231
dlist_head myProcLocks[NUM_LOCK_PARTITIONS]
Definition: proc.h:257
ProcWaitStatus waitStatus
Definition: proc.h:163
dlist_node links
Definition: proc.h:159
LOCK * myLock
Definition: lock.h:365
PGPROC * myProc
Definition: lock.h:366
Definition: lock.h:370
LOCKMASK holdMask
Definition: lock.h:376
dlist_node lockLink
Definition: lock.h:378
PGPROC * groupLeader
Definition: lock.h:375
LOCKMASK releaseMask
Definition: lock.h:377
PROCLOCKTAG tag
Definition: lock.h:372
dlist_node procLink
Definition: lock.h:379
PGPROC * allProcs
Definition: proc.h:380
uint32 allProcCount
Definition: proc.h:398
LOCKTAG locktag
Definition: lock.c:159
LOCKMODE lockmode
Definition: lock.c:160
LocalTransactionId localTransactionId
Definition: lock.h:62
ProcNumber procNumber
Definition: lock.h:61
dlist_node * cur
Definition: ilist.h:179
dlist_node * cur
Definition: ilist.h:200
dlist_node * next
Definition: ilist.h:140
Definition: type.h:95
TransactionId xid
Definition: lockdefs.h:51
#define InvalidTransactionId
Definition: transam.h:31
#define FirstNormalObjectId
Definition: transam.h:197
#define TransactionIdIsValid(xid)
Definition: transam.h:41
void RegisterTwoPhaseRecord(TwoPhaseRmgrId rmid, uint16 info, const void *data, uint32 len)
Definition: twophase.c:1280
int max_prepared_xacts
Definition: twophase.c:115
TransactionId TwoPhaseGetXidByVirtualXID(VirtualTransactionId vxid, bool *have_more)
Definition: twophase.c:852
PGPROC * TwoPhaseGetDummyProc(TransactionId xid, bool lock_held)
Definition: twophase.c:918
#define TWOPHASE_RM_LOCK_ID
Definition: twophase_rmgr.h:25
const char * type
bool RecoveryInProgress(void)
Definition: xlog.c:6290
#define XLogStandbyInfoActive()
Definition: xlog.h:121
bool InRecovery
Definition: xlogutils.c:50
#define InHotStandby
Definition: xlogutils.h:57
static struct link * links
Definition: zic.c:299